One of the most persistent myths about war is that it is sometimes inevitable. States are carried along by the impersonal forces of history: the balance of power, alliance commitments, ideological antagonisms, the rise and decline of great powers, et cetera. Leaders may make mistakes along the way, but these are trivia, for the ultimate outcome was determined by circumstances beyond their control.
And while it is true the international environment constrains the choices available to statesmen, sometimes severely, constraints are not immutable laws, and circumstances do not make decisions. But the false and persistent narratives are politically useful to the powerful, for the invocation of historical necessity serves to excuse the decisions of those who possess the power to make war and obfuscate their ultimate responsibility for having failed to do otherwise.
Looking at the outbreak of war through the lens of libertarian realism helps one to better see this fact. In it, the application of the normative commitment to individual liberty and the non-aggression principle to foreign affairs is coupled with a public-choice analysis of why political decisionmakers chose to intervene. This latter facet helps us see the state not as a unitary actor pursuing some objectively identifiable national interest, but as individuals facing an incentive structure featuring a range of possible alternatives, some serving their interests and others not. By looking at individual decision makers and the choice architecture they faced, it asks who actually made a decision, what alternatives were available, and whose interests were served.
Two of history’s most consequential conflicts, the Peloponnesian War and the First World War, illustrate the value of this approach. In both cases, structural explanations have overwhelmingly tended to overshadow the proximate decisions that converted political disputes into catastrophic wars. In both cases, however, domestic political calculations go a long way in helping explain why leaders chose escalation rather than accommodation.
Thucydides famously attributed the Peloponnesian War to the growth of Athenian power and the fear this inspired in Sparta. This remains one of the most influential structural explanations of international conflict—the so-called “Thucydides Trap.” As Athens grew stronger, Sparta became increasingly apprehensive; eventually, the relationship between the two powers became intolerable.
There is considerable truth in this account. Athenian imperial expansion, the competing interests of the two alliances, and the demands of Athens’s allies created genuine sources of tension. Corinth, in particular, pressed Sparta to confront Athens, while disputes involving Corcyra, Potidaea, and Megara threatened to destabilize an already precarious peace.
But explaining the conditions under which war became possible is not the same as explaining why it actually occurred. The existence of rivalry does not make armed conflict inevitable. Statesmen still have to decide whether to compromise, negotiate, threaten, mobilize, or fight.
Here Plutarch’s Life of Pericles offers an important corrective to an overly structural interpretation of the commencement of war. His account places the domestic political position of Athens’s leading statesman squarely within the story of the war’s origins.
Pericles was hardly an ordinary politician. He had presided over the expansion of Athenian power and enjoyed extraordinary influence over the city’s democratic institutions. Yet that influence did not render him immune to political opposition. His associates faced accusations and prosecutions, including the controversial sculptor Phidias, who had been entrusted with the construction of the statue of Athena in the Parthenon. Aspasia, Pericles’s companion, was also accused of impiety, while the philosopher Anaxagoras became another target of hostility associated with the political circle surrounding him.
Plutarch connects these controversies to the confrontation with Sparta—specifically, via Pericles’s refusal to repeal the Megarian Decree, which excluded Megarian merchants from the Athenian agora and ports within the Athenian sphere of influence, and which was politically very popular. The decree became a major grievance among Sparta’s allies and one of the disputes surrounding the outbreak of war.
Strikingly, Plutarch foregrounds the details of this case against Pericles with the conventional structure explanations for the “inevitable” outbreak of war, and is dismissive of these, giving the most seeming credence to “the worst motive of all, which is confirmed by most witnesses.” According to this account, Pericles faced a political predicament: the prosecution of his associates threatened to implicate his own administration, and the possibility of further concessions to Sparta risked making him appear weak. A foreign confrontation offered an opportunity to redirect public attention and demonstrate his indispensability to Athens.
The same analytical error appears in orthodox explanations of Britain’s entry into the First World War. The familiar account emphasizes German militarism, the European balance of power, the Entente with France and Russia, and the German invasion of Belgium. Each matters. None, however, eliminates the need to explain why British leaders chose intervention when they did.
Britain was not attacked by Germany in July 1914. Its relationship with France rested on understandings, military conversations, and strategic cooperation rather than an unambiguous treaty requiring Britain to enter a continental war. The 1839 Treaty of London, to which London was a signatory and which guaranteed Belgian neutrality among the signers, retroactively provided an important legal and political basis for intervention after German forces invaded Belgium. But the treaty did not stipulate British entry upon a war to uphold Belgian neutrality, and whether intervention was justified simply because Germany violated Belgian neutrality is a separate question that can be put aside.
The more immediate question is why intervention became the British government’s chosen policy despite serious divisions within the cabinet, lack of support in the majority in Parliament, and the absence of any great public demand for war.
The domestic political context deserves considerably more attention than it commonly receives, and provides a critical insight into the political factors driving decision-making among the leading British Liberals.
By the summer of 1914, Prime Minister Herbert Asquith’s Liberal government had already weathered a constitutional crisis over the passing of Irish Home Rule over and above the Lords, and now the implementation of the Home Rule Bill threatened to overthrow he and his party.
Facing the prospect of self-government in Ireland, Ulster Unionists, determined to resist inclusion in a Dublin-based administration, had organized an armed movement. Irish nationalists were mobilizing in response. The prospect of civil conflict was real, and the government’s authority had been badly tested. Indeed, the Curragh incident of March 1914 had exposed the limits of that authority. British army officers, who were overwhelmingly conservative and opposed to Irish Home rule, indicated their unwillingness to enforce Home Rule against Ulster Unionists.
This forced the government into an embarrassing retreat, raising profound questions about civilian control of the military, and suggesting that were home rule to be enforced it would take the deployment of Britain’s actual army, small though it was, to Ireland. When the Buckingham Palace Conference failed to resolve the Irish question, it did so against the backdrop of the mounting July Crisis on the Continent. Thus, as the European crisis unfolded, Asquith’s government faced a potentially explosive domestic confrontation and a rapidly deteriorating international situation.
War offered the Liberal government a means of postponing the Irish confrontation, redirecting political attention, and maintaining its hold on power. For their part, the Conservatives were inclined toward war, even if it meant supporting Asquith, for it was understood that having but a single small army it could be deployed to Ireland to enforce home rule or to the Continent to support the Entente, but not both. War even secured Asquith cooperation of Irish parliamentary nationalists. On August 3, the day before Asquith’s government declared war on Germany, John Redmond, leader of the Irish Parliamentary Party, offered support for the defense of Ireland while the crisis continued.
The Home Rule Bill was then suspended for the duration of the war.
These developments do not prove that Asquith entered the war solely to escape the Irish crisis. But we have no need to prove so much: the Irish question did not have to be the sole cause of intervention to be an important influence, perhaps the biggest influence, on the decisions of governments’ leading officials. The relevant question is whether the prospect of postponing domestic conflict, consolidating political support, and preserving the government’s position affected how its leaders evaluated the alternatives before them.
The libertarian realist is therefore dismissive of accounts that treat British intervention as the automatic expression of a disembodied national interest. Britain was not a person, and neither was the Liberal government. Asquith, Foreign Secretary Edward Grey, the anti-German clique in the Foreign Office (of whom an entire article on the causes of World War I could be devoted) and other ministers faced distinct political incentives and disagreed over the proper course of action. Their decision to intervene must be explained through those individuals and the institutions in which they operated, not simply through the strategic position of the British Empire.
Interestingly, even if Pericles sincerely believed that confrontation served Athenian security, and even if British ministers sincerely believed that intervention would preserve European stability, neither belief by itself establishes a moral entitlement to wage war. For the initiation of force requires justification. A state does not acquire a right to employ violence merely because its leaders believe that intervention would be strategically advantageous, that its prestige is at stake, or that a rival’s growing power is unsettling. Defensive force against aggression is morally different from intervention intended to preserve influence or impose a preferred political order.
This is not an argument that international structures are irrelevant, that leaders act without constraints, or that private motives explain everything. It is an argument against treating those as substitutes for political explanation. The task of the libertarian realist is not merely to identify the conditions under which war became possible, but to explain why particular individuals chose it when alternatives remained available.
That distinction matters beyond the study of ancient Greece or Edwardian Britain. Contemporary leaders routinely describe prospective conflicts as inevitable, whether because of great-power competition, alliance commitments, or the need to preserve national credibility. Such claims deserve skepticism. They can obscure the choices already made, conceal the interests served by escalation, and prepare the public to accept a war that might otherwise be resisted.
Wars are not made by abstractions. They are made by people—and people who choose war must be held accountable for the consequences.
