On June 28, 1914, a nineteen-year-old Bosnian Serb nationalist named Gavrilo Princip stepped from a café doorway in Sarajevo and fired two shots at Archduke Franz Ferdinand, heir to the Austro-Hungarian throne. Within six weeks, the six great powers of Europe were at war. Within four years, 20 million people were dead.

The remarkable thing about World War I is not that the assassination triggered war, but that the mechanisms linking a single murder to the mobilization of millions were so automatic, so interconnected, and so irreversible once set in motion. No major power genuinely wanted a European-scale war in August 1914. Yet they got one. The chancellor who sent Germany to war, Bethmann Hollweg, wrote in his diary that he felt he was "jumping into the dark." The Russian foreign minister Sazonov told the Tsar that war meant revolution and the fall of dynasties. The British foreign secretary, Sir Edward Grey, sat at his window the night the British ultimatum expired and said: "The lamps are going out all over Europe; we shall not see them lit again in our lifetime."

How does a murder in a Balkan city become a world war? How do rational actors produce catastrophically irrational outcomes? Why do wars start at all, given that they are costly for everyone involved?

These are the central questions of the political science of war — a field that has made substantial progress in understanding the mechanisms of armed conflict, even if it cannot predict specific wars.

"War is merely the continuation of politics by other means." — Carl von Clausewitz, On War (1832)

Key Definitions

War — Organized, sustained armed conflict between or within states. Definitions vary: most political science databases define interstate war as armed conflict between states with at least 1,000 battle deaths; civil war as armed conflict within a state with at least 1,000 battle deaths; and low-intensity conflict at lower thresholds. The definitional threshold matters because it determines which conflicts are counted and analyzed.

Interstate war — Armed conflict between sovereign states. Examples: World War I, World War II, Korea, the 1967 Arab-Israeli War, the Iran-Iraq War (1980-1988), the Gulf War (1990-1991). Historically the most studied form of war but relatively rare since 1945 compared to civil wars.

Civil war — Armed conflict within a state between the government and one or more non-state challengers, or between rival non-state groups. Examples: the American Civil War, the Spanish Civil War, the Rwandan Civil War, the Syrian Civil War. Far more common than interstate war in the post-1945 era and typically more destructive to civilian populations.

Bargaining model of war — The dominant theoretical framework in modern international relations, developed by James Fearon (1995). The model shows that since war is costly, rational actors should always prefer a negotiated settlement that produces a similar outcome at less cost. Wars occur when bargaining fails, typically due to private information, commitment problems, or issue indivisibility.

Security dilemma — The dynamic in which one state's moves to increase its security (building arms, forming alliances) make other states feel less secure, prompting them to respond in kind, ultimately leaving everyone less secure. Security dilemmas are a major source of arms races and a contributing factor to many wars, including World War I.

Democratic peace theory — The empirical finding (Michael Doyle, 1986; Bruce Russett, 1993) that democratic states rarely if ever go to war with each other. One of the most robust statistical findings in international relations. Explains why the liberal international order promotes democracy as a peace-building strategy.

Deterrence — The strategy of preventing adversary attack by threatening unacceptable costs in retaliation. Nuclear deterrence between the US and Soviet Union is credited with preventing a third world war. Deterrence requires capability (the ability to inflict the threatened costs) and credibility (the adversary believes you will use it).

Misperception — The phenomenon of leaders holding incorrect beliefs about adversary capabilities, intentions, or resolve, which can lead to miscalculated wars. Robert Jervis's Perception and Misperception in International Politics (1976) is the foundational work on how cognitive biases and information processing errors contribute to wars.

Audience costs — The domestic political costs a leader incurs from backing down from a publicly stated commitment. Democratic leaders face higher audience costs than autocrats because backing down is more visible and punishable. Audience costs theory (Fearon, 1994) explains why public commitments can affect crisis outcomes — and why leaders sometimes bluster themselves into wars they didn't initially want.

Offense-defense balance — Whether military technology at a given historical moment advantages offensive or defensive operations. When offense is believed to be advantaged, states have stronger incentives to strike first, "windows of vulnerability" are more dangerous, and arms races are more likely to produce war. Many historians argue that the early 20th century saw a mistaken belief in offense advantage that contributed to World War I.

Greed vs. grievance — The debate about motivations in civil wars. Paul Collier and Anke Hoeffler's influential research suggested that civil wars are better predicted by "greed" (opportunity — resource wealth enabling rebel financing) than "grievance" (political repression, inequality, ethnic discrimination). Later research by Cedric Atin and others found grievance factors more important than Collier and Hoeffler suggested.

Why Wars Happen: The Rationalist Puzzle

The Bargaining Problem

If war is costly for both sides — which it clearly is — why don't rational actors always negotiate a settlement rather than fight? This is the central puzzle that James Fearon's 1995 paper Rationalist Explanations for War formalized.

The logic: suppose two countries are about to go to war, and both know with certainty who will win and on what terms. The winner would prefer a negotiated settlement that gives them what fighting would yield, minus the costs of fighting. The loser would prefer a negotiated settlement that gives them what they'd get after losing, plus avoiding the costs of fighting. There exists a range of negotiated outcomes that both prefer to war.

If this logic is correct, war should never happen among rational actors. Yet wars happen constantly. Fearon's paper identifies three structural reasons why bargaining fails.

The empirical record gives striking weight to this puzzle. Reviewing 779 militarized interstate disputes between 1816 and 1992, Paul Senese and John Vasquez (2008) found that most were resolved short of war; the cases that escalated to war were systematically distinguishable by factors that impaired bargaining — repeated territorial disputes, rigid alliance commitments, and incomplete information about resolve. The rarity of war relative to the frequency of political conflict confirms that the baseline of international politics is actually negotiated compromise, and war represents a catastrophic failure of that baseline mechanism.

Reason 1: Private Information

States have private information about their capabilities, resolve, and intentions that they cannot credibly reveal to adversaries. A state about to lose a war has incentives to claim it is stronger than it is, hoping to negotiate better terms. This means adversaries discount each other's claims — they assume the other side is bluffing.

When neither side can credibly convey its true capabilities or resolve, bargaining reaches an impasse. War serves as a costly signal: only states that truly have strong capabilities or high resolve will be willing to pay the costs of fighting rather than accepting the negotiated terms the adversary offers.

This mechanism explains why wars are often preceded by crises during which communication fails. The Cuban Missile Crisis resolved peacefully partly because both Kennedy and Khrushchev found ways to credibly communicate their resolve and limits. Many other crises — including the July Crisis of 1914 — ended in war partly because communication channels were inadequate or messages were misread.

The Vietnam War offers a textbook illustration. American decision-makers from Kennedy through Johnson consistently underestimated the North Vietnamese government's willingness to absorb punishment (Daniel Ellsberg, 1972). The body counts that American strategists used as a proxy for progress were meaningless because Hanoi's resolve — rooted in the experience of decades of colonial war and a genuine nationalist movement — was not eroding as predicted. Private information about what the adversary would accept drove the war forward long past any rational calculation of likely outcome.

Reason 2: Commitment Problems

Even when parties reach a negotiated settlement, they may be unable to commit to honoring it. If State A is growing stronger relative to State B, B may prefer to fight now (when the balance is more favorable) rather than accept a deal that A will renegotiate from a stronger position in ten years. If A knows B is thinking this way, A may prefer to fight now rather than have B strike preemptively.

World War I is often analyzed as a commitment problem: Germany and Austria-Hungary feared Russia's rapid modernization would make it militarily dominant within a decade. Better to fight in 1914, when the balance was still manageable, than in 1924.

Japan's attack on Pearl Harbor (1941) has a similar structure: Japan's leaders feared that US rearmament would soon make Japan's position in East Asia militarily untenable. They chose war when the balance was still in their favor over accepting American demands that would constrain Japanese expansion indefinitely.

Commitment problems also explain why peace settlements sometimes fail. After the First World War, the Versailles settlement humiliated Germany without permanently disarming it, creating grievances that could be exploited once German strength recovered. A.J.P. Taylor (1961) and others noted that the peace imposed in 1919 was neither generous enough to be accepted nor harsh enough to permanently disable Germany — it created a window in which German revisionism, once armed, could challenge the settlement. The result was World War II.

Reason 3: Issue Indivisibility

Some issues cannot be divided or compromised. Sovereignty is the clearest example: a state either exists or it doesn't. Territory can sometimes be divided, but control of certain capital cities, religious sites, or ethnically mixed territories may be politically indivisible — neither side can accept a split because each sees the location as symbolically or strategically non-negotiable.

Jerusalem is the archetypal indivisible issue: both Israelis and Palestinians regard it as their capital; the symbolic and religious importance of the city makes compromise extremely difficult regardless of the strategic logic.

Monica Duffy Toft's research on civil wars (The Geography of Ethnic Violence, 2003) found that conflicts over territory with high ethnic concentration were significantly harder to resolve through negotiation than conflicts over policy or power-sharing. When a group believes that a particular piece of land is its homeland, no compensating payment can substitute — the group experiences the loss of territory as an existential threat to its identity and physical survival, making bargaining effectively impossible regardless of the rational logic.

The Role of Misperception

While Fearon's rationalist model explains many wars, it leaves out a critical factor: leaders are not perfectly rational. They misperceive, suffer from cognitive biases, and sometimes believe they are making good decisions based on incorrect information.

World War I: A War Nobody Wanted

The July Crisis of 1914 is the paradigmatic case of misperception producing catastrophe. Historians Barbara Tuchman (The Guns of August, 1962) and Christopher Clark (The Sleepwalkers, 2012) document how each step seemed rational in isolation, yet the collective outcome was a war that all major powers would have preferred to avoid.

Key misperceptions:

  • Austria-Hungary misjudged Serbia's willingness to accept humiliating terms after the assassination
  • Germany misjudged Britain's willingness to enter the war over Belgium
  • All parties misjudged how quickly the war would escalate and how long it would last ("home by Christmas")
  • The German military's Schlieffen Plan — designed to avoid a two-front war by quickly defeating France before turning to Russia — required an incredibly rigid timetable that made mobilization nearly irreversible once begun

Robert Jervis's classic analysis identifies the cognitive mechanisms that make misperception systematic: motivated reasoning (we tend to believe what we want to believe), mirror imaging (assuming adversaries think like us), and attribution errors (we attribute our own actions to circumstances but adversary actions to hostile intent).

The Psychology of Escalation

Research by social psychologists Philip Zimbardo and Philip Tetlock adds an important dimension to misperception: leaders in crisis conditions face acute stress, information overload, and time pressure that systematically degrade judgment. Tetlock's studies of expert forecasters (2005) found that most political "experts" performed barely better than random chance on geopolitical predictions, because they applied rigid mental models to complex adaptive systems.

During crises, several psychological biases interact destructively. Groupthink, identified by Irving Janis (1972) through analysis of the Bay of Pigs disaster, occurs when cohesive decision-making groups suppress dissent, share illusions of invulnerability, and fail to consider the full range of options. Prospect theory, developed by Daniel Kahneman and Amos Tversky (1979), shows that decision-makers in a domain of perceived loss are more willing to take risks than rational expected-utility theory would predict — leaders who believe they are losing may escalate rather than accept a negotiated outcome that acknowledges the loss.

"The most important decisions — on war and peace — are made under conditions where policymakers are stressed, fatigued, and operating on incomplete information. The conditions least conducive to careful deliberation are precisely those under which deliberation matters most." — Robert Jervis, Perception and Misperception in International Politics (1976)

The combination of structural factors (commitment problems, private information) and psychological factors (misperception, cognitive bias) means that understanding why wars start requires both the rationalist toolkit of political science and the behavioral toolkit of psychology.

Causes of Modern Wars

The Democratic Peace

One of the most robust findings in the quantitative study of war is the democratic peace: democracies almost never go to war with other democracies. Between 1816 and 2005, there are fewer than a handful of wars between states that both qualify as liberal democracies by most definitions.

Three explanations have been proposed:

Normative/cultural: Democracies share norms of peaceful conflict resolution and mutual recognition of legitimacy. They extend to other democracies the expectation that conflicts will be resolved through negotiation rather than force.

Institutional: Democratic leaders face institutional constraints (legislative approval, electoral accountability) that make initiating war more costly. Democratic leaders who start wars they lose face removal from power; this creates caution.

Economic: Democracies tend to be more economically interdependent with each other, raising the economic costs of war.

The democratic peace does not mean democracies are peaceful in general — they fight non-democracies at roughly the same rate as other state types. It is specifically the dyadic relationship between two democracies that is peaceful.

However, recent scholarship has complicated the picture. John Owen IV (1994) argued the democratic peace is real but narrow — liberal democracies are peaceful with each other specifically because they perceive each other as liberal. Democracies that perceive a rival as illiberal (even if formally democratic) do not extend the same restraint. Bruce Bueno de Mesquita and colleagues (2003) proposed the selectorate theory, arguing that what matters is not democracy per se but the size of the "winning coalition" of supporters a leader needs to maintain power — larger winning coalitions make war less attractive because its costs are distributed more widely.

Access to natural resources has driven conflicts throughout history. The logic of "resource wars" is straightforward: states may go to war to control valuable resources — oil, water, fertile land, minerals — when the expected gain from control exceeds the cost of fighting.

But the statistical relationship between resources and conflict is more complex. Paul Collier and Anke Hoeffler's research found that countries with high dependence on primary commodity exports had dramatically higher risk of civil war — not because of interstate conflict, but because resource wealth enables rebel groups to finance insurgencies.

Countries that export oil, diamonds, or other easily "lootable" resources are more conflict-prone: the resource provides both a prize for rebels and a financing mechanism. This resource curse — the counter-intuitive finding that resource wealth correlates with instability and poor governance — is one of the most extensively studied phenomena in development economics.

The numbers are striking. Collier and Hoeffler (2004) found that countries where primary commodity exports constituted 28% of GDP faced a 33% probability of civil war onset over any five-year period — compared to roughly 1% for countries with no such exports. Sierra Leone's decade-long civil war (1991-2002) was financed almost entirely through diamond mining by the Revolutionary United Front; the war killed 50,000 people and displaced 2 million. The Democratic Republic of Congo has experienced persistent conflict in its mineral-rich eastern provinces, where coltan (used in consumer electronics), gold, and cassiterite have funded dozens of armed groups across three decades of intermittent warfare.

Water scarcity has increasingly attracted attention as a future driver of conflict. A 2019 study by Tobias Ide and colleagues published in Global Environmental Change found that water insecurity was a statistically significant predictor of armed conflict onset after controlling for other factors, though the relationship operated primarily through economic stress and state fragility rather than direct "water wars." The Nile River basin — shared by Ethiopia, Sudan, and Egypt — presents one of the most acute near-term water conflict scenarios as Ethiopia's Grand Ethiopian Renaissance Dam alters downstream flow to Egypt, a country that uses the Nile for 90% of its fresh water.

Nuclear Deterrence and the Long Peace

Since 1945, there has been no direct military confrontation between nuclear-armed great powers — the United States, Russia, China, UK, France, India, Pakistan, Israel, and North Korea. This Long Peace (John Lewis Gaddis's term) is remarkable given the number and severity of crises.

The standard explanation is nuclear deterrence: the mutual certainty of catastrophic destruction makes war between nuclear states too costly to contemplate. MAD (Mutually Assured Destruction) stabilized the US-Soviet standoff during the Cold War by ensuring that any nuclear first strike would produce a retaliatory second strike that would destroy the attacker.

Nuclear deterrence is not foolproof. The Cuban Missile Crisis of 1962 brought the world closer to nuclear war than the public knew — multiple accidents and close calls occurred during the 13-day standoff. On October 27, 1962, Soviet submarine B-59 was out of communication with Moscow, believed it was at war, and came within one officer's dissent of launching a nuclear torpedo. Vasili Arkhipov, the submarine's flotilla commander, refused to authorize the launch; he is credited by some historians with preventing nuclear war that day. But the deterrent relationship has so far held, and its contribution to great-power peace is widely credited.

The stability of nuclear deterrence depends critically on leadership rationality and command-and-control reliability. As nuclear arsenals spread to states with less sophisticated command structures (Pakistan, North Korea), the assumptions underlying deterrence theory come under increasing stress. Scott Sagan's research (The Limits of Safety, 1993) documented dozens of near-accidents in the American nuclear arsenal despite elaborate safety procedures, raising questions about whether states with younger, less institutionalized nuclear programs can maintain the same safety record.

Civil Wars: The Dominant Form of Modern Conflict

Since 1945, civil wars have been far more common than interstate wars and have produced far more casualties. The Syrian Civil War (400,000-600,000 deaths), the Second Congo War (3-5 million deaths), the Rwandan Genocide (800,000 deaths in 100 days), and the Yugoslav wars of the 1990s have dominated post-Cold War conflict.

The causes of civil war differ from interstate war in important ways:

State capacity: Weak states with limited administrative and coercive capacity are far more prone to civil war. When the state cannot effectively govern its territory, armed groups can challenge it.

Ethnic and religious cleavages: While ethnicity alone does not cause war (most multiethnic states are peaceful), ethnic or religious identities can be mobilized to recruit fighters and provide organizational structure for rebel movements.

Economic underdevelopment: Poor countries with high youth unemployment and limited economic opportunities provide a ready supply of potential combatants.

External support: Civil wars are sustained and intensified by external actors providing arms, financing, and sanctuary. The Cold War made many civil wars proxy conflicts between the superpowers.

James Fearon and David Laitin's landmark 2003 study in American Political Science Review found that the strongest predictors of civil war onset were per capita income (lower income dramatically increased risk), mountainous terrain (which provides sanctuary for insurgents), and political instability — not ethnic or religious diversity per se. Countries with these structural conditions remained conflict-prone regardless of ethnic composition. This finding challenged popular assumptions that ancient ethnic hatreds drove civil wars and pointed instead toward structural and political explanations amenable to policy intervention.

Conflict Duration Deaths Type Primary Cause
World War I 1914-1918 ~20 million Interstate Alliance commitments, security dilemma, miscalculation
World War II 1939-1945 ~70-85 million Interstate Fascist expansion, appeasement failure
Korean War 1950-1953 ~3-4 million Interstate + civil Cold War proxy, miscalculation
Vietnam War 1955-1975 ~1.5-3.5 million Civil + interstate Cold War proxy, nationalist insurgency
Second Congo War 1998-2003 ~3-5 million Civil (internationalized) State collapse, resource competition
Syria 2011-present ~400,000-600,000 Civil + interstate proxy Authoritarian repression, Arab Spring, external intervention
Ukraine 2022-present Ongoing Interstate Russian territorial expansion, NATO expansion

Hybrid Warfare and the Changing Character of Conflict

The strict categories of war — interstate, civil, guerrilla — have been complicated in the contemporary era by the emergence of hybrid warfare: strategies that combine conventional military operations with cyber attacks, information operations, economic coercion, support for proxy forces, and political manipulation, all designed to achieve strategic objectives below the threshold of declared war.

Russia's actions in Ukraine before and during its full-scale 2022 invasion exemplified hybrid warfare: seizing Crimea in 2014 with troops in unmarked uniforms ("little green men"), supporting separatist forces in the Donbas with deniable military assistance, conducting sustained cyber attacks against Ukrainian infrastructure (including the 2015 and 2016 attacks on Ukraine's power grid — the first confirmed cyber attacks to cause physical infrastructure failures), and conducting information operations targeting Ukrainian political cohesion. The ambiguity was strategic: hybrid methods sought to create facts on the ground while maintaining plausible deniability and staying below the threshold that would trigger NATO collective defense.

Frank Hoffman, who coined the term hybrid warfare in 2007, defined it as the use of "a full complement of conventional weapons, irregular tactics, terrorism, and criminal behavior in the same time and battlespace." The challenge for deterrence theory is that hybrid warfare erodes the clear thresholds on which classical deterrence depends — an adversary may achieve substantial strategic gains without crossing the line that would trigger a formal military response.

Cyber operations occupy a particularly uncertain space in the laws of war and deterrence strategy. The 2017 NotPetya malware attack — attributed to the Russian military intelligence agency GRU — spread from Ukrainian targets to become the most destructive cyber attack in history, ultimately causing approximately $10 billion in damage globally. It affected Maersk shipping, FedEx, hospitals, and banks across dozens of countries. Whether this constituted an act of war by any meaningful definition remained officially unresolved, and no military response was forthcoming. This impunity likely shaped subsequent adversary calculations about what cyber operations were permissible.

Can War Be Prevented?

The liberal peace theory holds that a combination of factors systematically reduces war probability:

  • Democratic governance: Democracies don't fight each other
  • Economic interdependence: Trading partners have economic incentives to avoid war
  • International institutions: The UN, WTO, and other bodies create rules, forums for dispute resolution, and costs for rule-breaking
  • Nuclear deterrence: Among nuclear powers, mutual destruction threat prevents direct war

This combination has produced remarkable great-power peace since 1945. But it has not eliminated war — it has displaced conflict toward civil wars, proxy wars, and hybrid warfare (combining military operations with cyber attacks, election interference, and economic coercion below the threshold of conventional war).

Steven Pinker's The Better Angels of Our Nature (2011) marshaled extensive statistical evidence that violence of all kinds — interstate war, civil war, homicide, torture — has declined dramatically over the long run of human history. His key argument was that the Enlightenment, the expansion of trade, the growth of literacy and empathy, and the development of international institutions had collectively shifted human psychology and incentive structures away from violence.

Critics challenged both Pinker's data and his conclusions. Nassim Nicholas Taleb argued that the statistics are distorted by the absence of the truly catastrophic wars that become possible with nuclear and biological weapons — that we are in a "peace" that is maintained by deterrence stability that could break down catastrophically. John Gray argued that Pinker's progressive narrative is fundamentally ideological, obscuring the ways in which Enlightenment rationalism produced its own forms of mass killing (the Terror, colonial conquest, scientific racism). Bear Braumoeller's Only the Dead (2019) offered the most systematic statistical challenge, arguing that when controlling for the number of states and opportunity for war, the post-World War II era does not show a statistically significant decline in the rate of war — what has declined is the average size of states' populations relative to the scale of industrial warfare.

The debate matters practically. If the decline of war is robust and driven by identifiable factors, international policy can reinforce those factors. If it reflects idiosyncratic post-1945 conditions — nuclear deterrence, American hegemony, European exhaustion — that could unravel, the basis for optimism is shakier.

"The hope for durable peace is not that states will suddenly become unselfish, but that they will realize that in the contemporary world, war tends to be less profitable and more catastrophic than the alternatives." — Bruce Russett, Grasping the Democratic Peace (1993)

The persistence of war in the modern era reflects the persistence of the conditions that produce it: resource competition, security dilemmas, commitment problems, misperception, and the willingness of some leaders to pay the costs of war to achieve their objectives. What political science offers is not a cure but a diagnosis — a set of structural factors and mechanisms whose recognition is a precondition for managing them.

For related concepts, see US-China rivalry explained, Iran-Israel conflict explained, and how oil shapes geopolitics.

References

  • Fearon, J. D. (1995). Rationalist Explanations for War. International Organization, 49(3), 379-414. https://doi.org/10.1017/S0020818300033324
  • Fearon, J. D., & Laitin, D. D. (2003). Ethnicity, Insurgency, and Civil War. American Political Science Review, 97(1), 75-90. https://doi.org/10.1017/S0003055403000534
  • Jervis, R. (1976). Perception and Misperception in International Politics. Princeton University Press.
  • Tuchman, B. W. (1962). The Guns of August. Macmillan.
  • Clark, C. (2012). The Sleepwalkers: How Europe Went to War in 1914. HarperCollins.
  • Clausewitz, C. von. (1832). On War. Ed. and trans. M. Howard and P. Paret. Princeton University Press (1976).
  • Doyle, M. W. (1986). Liberalism and World Politics. American Political Science Review, 80(4), 1151-1169. https://doi.org/10.2307/1960861
  • Russett, B. (1993). Grasping the Democratic Peace. Princeton University Press.
  • Collier, P., & Hoeffler, A. (2004). Greed and Grievance in Civil War. Oxford Economic Papers, 56(4), 563-595. https://doi.org/10.1093/oep/gpf064
  • Pinker, S. (2011). The Better Angels of Our Nature: Why Violence Has Declined. Viking.
  • Gaddis, J. L. (1986). The Long Peace: Elements of Stability in the Postwar International System. International Security, 10(4), 99-142.
  • Senese, P. D., & Vasquez, J. A. (2008). The Steps to War: An Empirical Study. Princeton University Press.
  • Toft, M. D. (2003). The Geography of Ethnic Violence: Identity, Interests, and the Indivisibility of Territory. Princeton University Press.
  • Tetlock, P. E. (2005). Expert Political Judgment: How Good Is It? How Can We Know? Princeton University Press.
  • Kahneman, D., & Tversky, A. (1979). Prospect Theory: An Analysis of Decision under Risk. Econometrica, 47(2), 263-292. https://doi.org/10.2307/1914185
  • Sagan, S. D. (1993). The Limits of Safety: Organizations, Accidents, and Nuclear Weapons. Princeton University Press.
  • Hoffman, F. G. (2007). Conflict in the 21st Century: The Rise of Hybrid Wars. Potomac Institute for Policy Studies.
  • Braumoeller, B. F. (2019). Only the Dead: The Persistence of War in the Modern Age. Oxford University Press.
  • Ide, T., Brzoska, M., Donges, J. F., & Schleussner, C. F. (2020). Multi-method evidence for when and how climate variability contributes to armed conflict risk. Global Environmental Change, 62, 102063.
  • Ellsberg, D. (1972). Papers on the War. Simon and Schuster.
  • Janis, I. L. (1972). Victims of Groupthink. Houghton Mifflin.

Tags

war conflict political science international relations geopolitics history peace

Frequently Asked Questions

Why do countries go to war instead of negotiating?

The bargaining model of war explains that wars are costly for both sides, yet they occur when negotiation fails. Bargaining typically fails for three reasons: private information (each side has secrets it cannot credibly reveal), commitment problems (agreements cannot be reliably enforced), and issue indivisibility (some things, like sovereignty, cannot be divided). Wars resolve these failures through costly demonstration of resolve and capability.

Is war declining over time?

The evidence is mixed. Steven Pinker's 'Better Angels' thesis argues that violence per capita has declined dramatically over millennia. Joshua Goldstein shows interstate war deaths have declined since 1945. But scholars like Bear Braumoeller challenge this, arguing the absence of great-power war since 1945 is fragile, and conflict in the 21st century has shifted toward civil wars, terrorism, and hybrid warfare.

What role does misperception play in causing wars?

Many wars are attributed to misperception — leaders miscalculating adversary intentions, capabilities, or resolve. World War I is often cited as a war no major power wanted but all stumbled into through serial miscalculations. The Falklands War began partly because Argentina misread British resolve to defend a distant territory. Misperception is particularly dangerous because it suggests wars can occur even when both sides would prefer to avoid them.

Do democracies go to war less often?

The Democratic Peace Theory (Doyle, 1986; Russett, 1993) is one of the most robust findings in international relations: democracies very rarely fight each other. However, democracies fight non-democracies at similar rates to other state types. The explanation is debated: shared norms of conflict resolution, mutual recognition of legitimacy, economic interdependence, or the institutional constraints on democratic leaders starting wars.

Why does the Ukraine-Russia war matter globally?

Russia's 2022 invasion of Ukraine is the largest conventional war in Europe since 1945. It challenges the post-WWII principle that borders cannot be changed by force, tests the deterrence value of NATO membership, has reshaped European energy security, and demonstrated both the persistence and limits of conventional military power. Its outcome will shape great-power competition for decades.

What is the difference between interstate and civil war?

Interstate wars are between sovereign states; civil wars are armed conflicts within a state between government forces and non-state challengers, or between rival groups. Since 1945, civil wars have been far more common than interstate wars. Civil wars are typically longer, more destructive to civilians, and harder to end through negotiation. Many civil wars have international dimensions (foreign intervention, arms supply).

Can war be prevented?

Political science identifies several factors associated with reduced conflict: democratic institutions, economic interdependence, international institutions and norms, nuclear deterrence (among great powers), effective communication channels, and third-party mediation. No single factor guarantees peace, but combinations of these factors have maintained remarkable great-power peace since 1945.

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