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.