Although President Trump is under fire for allegedly mocking the sacrifice of American soldiers who died in past conflicts abroad, his repeated grumbling about “endless wars” is also worth taking seriously. Since he reads little history, he may not know that his skepticism about foreign intervention belongs to a long national tradition: There has been spirited resistance to every major conflict the United States has waged, with the exception of the Second World War. Even then, millions of Americans wanted to stay out of the war, until the Japanese attack on Pearl Harbor made a peaceful solution utterly impossible.

But those who oppose military intervention have almost always been motivated by sharply different ideological beliefs. Conservatives like Trump seek to protect “America First” (and only) and bridle at costly missions to save the world. Most liberals and leftists, on the other hand, aim to build a global order based on peaceful cooperation and democratic rule and view armed force as a major obstacle to that end.

During a discussion over World War I, Trump reportedly questioned “who the good guys” were and slammed the doughboys who died in France as “losers” and “suckers.”

These doubts existed as the United States debated entry into the war. Liberals organized resistance to American entanglement. They argued that the bloodshed would just enrich munitions companies and big banks and might turn the United States into a militaristic society. Reformer Jane Addams led a delegation of feminists to Europe where she presided over a Congress of Women from 12 nations. They resolved to “retain our solidarity” and “mutual friendship” across the same frontiers that millions of men were slaughtering each other to maintain. Inside the Capitol, Sen. George Norris a liberal Republican from Nebraska, charged, “We are going into war on the command of gold. … We are about to put the dollar sign upon the American flag.”

But Americans on the right weren’t uniform supporters of the war either. They raised a different kind of protest once President Woodrow Wilson took the nation into the conflict, vowing that “the world must be made safe for democracy.” Sen. James Vardaman (D-Miss.), a hardened racist, warned that Black soldiers trained to kill the enemy would pose a “horrible problem” for his region. After the war ended, a conservative bloc of senators, led by Henry Cabot Lodge, defeated ratification of the Versailles peace treaty because it included an article obliging members of the new League of Nations to protect one another from “external aggression.” U.S. troops should be used, Lodge and his allies argued, to defend only America from attack or enhance its economic prospects.

Twenty years later, that same logic fueled the growth of the America First Committee, a largely Republican group that included a sprinkling of left-wing populists. The committee clamored to keep the United States out of the next world war that was raging in Europe and Asia. At its zenith, the group boasted some 800,000 members. Its popularity was driven by the view of most Americans that it had been a mistake to intervene in World War I. Reflecting the political potency of this thinking, Congress, by overwhelming majorities, had passed neutrality acts in the late 1930s that placed an embargo on selling or loaning money to belligerents. As Benito Mussolini and Adolf Hitler took aggressive moves against their neighbors, the bills prevented President Franklin D. Roosevelt from doing anything substantial to stop them.

But then, in September 1941, Charles Lindbergh, the leading spokesperson for America First and the son of a congressman who had opposed World War I, accused the British, Roosevelt and Jews of having a “large ownership and influence in our motion pictures, our press, our radio and our government.” He claimed they were all trying to pull the United States into another senseless European quarrel. The organization never recovered from this airing of his anti-Semitic views and disbanded entirely after the attack on Pearl Harbor in December 1941. But decades later, such prominent paleoconservatives as Patrick Buchanan revived the America First slogan and even labeled the Second World War an “unnecessary” conflict.

On the left, the sole group of Americans who took a public stand against intervention in World War II were pacifists, who detested state violence in any form. A few, like the Black civil rights activist Bayard Rustin, served years in federal prison for refusing to submit to conscription.

The Cold War posed a dilemma for anti-interventionists on the right. As haters of communism, they supported the creation of NATO and strongly endorsed the wars in Korea and Vietnam. But the libertarians among them viewed the draft as an assault on individual rights. At the convention of Young Americans for Freedom in 1969, some members burned their draft cards to protest the heavy hand of the state — and were quickly expelled from the organization. Most conservatives at the time backed the cause of the Saigon regime to the hilt and still blamed Democrats in Congress for cutting off its funding, which sped the victory of North Vietnam. By that time, nearly all liberals had turned against a war that radicals had been opposing for over a decade.

The collapse of the Soviet Union and its empire, perhaps inevitably, revived the old arguments, on both sides, against sending American troops into combat. Paleoconservatives and stalwart leftists both lambasted the invasion of Iraq in 2003. Buchanan and his allies were incensed that “a cabal of polemicists and public officials … were colluding with Israel to ignite” that war while socialist Noam Chomsky and his ilk thought it was the Middle Eastern nation’s “massive petroleum resources” that drove the George W. Bush administration to topple Saddam Hussein.

Trump’s retrospective aversion to the Iraq War and the ongoing one in Afghanistan may have helped him win the presidency in 2016. But it is driven more by the failure to achieve the stated objectives of those who initiated them than by deep-seated ideals or a coherent foreign policy philosophy. As with every other matter, the president thinks only about the benefit or damage a war is doing, or would do, to his self-interest — whether in business or politics.

The military enthralls him, as evidenced by his often bellicose rhetoric, though he himself used a minor ailment to get out of the draft at the height of the Vietnam War.

Still, Trump in his crass and unintentional way, has stumbled on a truth that might shock many Americans: With the exception of the Second World War, every major war the United States has fought over the past century has been a war of choice. Even the 2001 toppling of the Taliban’s rule in Afghanistan — the original purpose of the invasion meant to revenge the attacks of Sept. 11, 2001 — could have been accomplished with military aid to local militias that opposed the regime.

And neither Imperial Germany, North Korea, North Vietnam, nor Saddam Hussein posed a vital threat either to our economic well-being or to our national security. Taken together, the consequence of all these wars has been a permanent military establishment whose current cost easily dwarfs that of every other nation. It also defines “service to the nation” as an ideal one can pursue only with a uniform on and a gun close at hand. As long as it remains true, it will be difficult to break from our tradition of “endless” armed conflicts.