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Why America Fought

The lessons of World War I

Aug 11, 2014, Vol. 19, No. 45 • By DAVID ADESNIK
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The United States entered the Great War with its eyes wide open. The mechanical slaughter in Europe had already left millions dead. In the trenches, men had to contend with lice, rats, sickness, mud, extreme temperatures, human waste, rotting corpses, and boredom as well as the threats of poison gas, explosive shells, and being buried alive. In 1914, Europe went to war with only the dimmest awareness of the horrors to come. Yet Congress voted overwhelmingly for a declaration of war in the absence of any direct threat to U.S. territory and despite the country’s long tradition of distancing itself from European wars. What could explain both the American government’s decision and the broad and deep popular support for the war?


Today, even a well-rounded college graduate is unlikely to know more about American intervention than the fact that it had something to do with German submarines. Yet why did the United States send two million men to fight in France and Belgium after the Germans sank a handful of merchant vessels? The answer is that Americans across the political spectrum believed they were fighting to defend their inalienable rights, which included the freedom of the seas. If the United States let the German empire trample on its rights, this weakness would invite other challenges. There seemed to be no option but war.

By the 1930s, however, a new consensus portrayed American intervention as a tragic and wasteful misadventure. The Allies’ hollow victory did not bring peace, but only pervasive fears of a more destructive war to come. In today’s terminology, Americans retroactively redefined intervention in the Great War as a choice, not a necessity. The simplistic distinction between wars of choice and wars of necessity, however, only clouds our understanding of the past and its lessons for today. If one revisits 1917 without these conceptual blinders on, what begins to emerge is a deeper understanding of what Americans, in any time and place, believe is worth fighting for.

Wars of Necessity, Wars of Choice

In theory, wars of necessity have a justification so compelling that there is effectively no choice but to fight. World War II provides the paradigmatic example. For the United States, however, wars of necessity are the exception, not the rule. The label does not account for the War of 1812, the Mexican-American War, the Spanish-American War, the Korean War, Vietnam, the invasions of Panama and Grenada, or George W. Bush’s war in Iraq. It certainly does not account for humanitarian interventions. Even George H. W. Bush’s war in Iraq does not measure up. General Colin Powell, then serving as chairman of the Joint Chiefs of Staff, opposed the decision to fight. So did 47 senators, whereas only 23 voted against the war to oust Saddam Hussein.

In early 2003, the distinction between wars of choice and necessity earned its place in our political lexicon because it seemed to capture the difference between the invasion of Afghanistan and the impending war with Iraq. In 2009, President Obama justified the dispatch of additional troops to Afghanistan by insisting it remained a war of necessity, yet within months he had shifted to emphasizing his interest in ending the war. Hindsight transformed a necessity into a choice, as it had after World War I.

To dispel this confusion, the place to begin is with the old saw that war should always be the option of last resort. The question is, The last resort before what? The answer depends greatly on both Americans’ understanding of their role in the world and their assessment of other countries’ capabilities and intentions. This is the real terrain on which a debate about war and peace should take place.

The Meaning of American Neutrality, 1914-1916

In response to the outbreak of war in Europe, President Woodrow Wilson implored Americans to be “impartial in thought as well as in action.” This high-minded sentiment was impractical not just in terms of psychology, but, more important, in terms of geography and technology. According to diplomatic convention, neutral powers had a right to commerce with all belligerents, including the right to sell munitions and war materiel. In practice, Britain’s naval supremacy ensured that only the Allies would have access to the American arsenal. Germany soon discovered that submarines were the only means of disrupting the commerce that sustained the Allies’ war effort.

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