By Mark Dubowitz, CEO of the Foundation for Defense of Democracies and David Adesnik, director of research at the Foundation for Defense of Democracies

Donald Trump has been telling us since the first day of his presidency that the American president should no longer be the leader of the free world and that he personally has no interest in the job. This month, he made good on his words by unleashing chaos in northern Syria.

Trump’s actions empowered American adversaries ranging from the Islamic State militant group to Iran, Russia, Turkey and the regime of Syrian leader Bashar al-Assad and abandoned the local Syrian forces, especially Kurdish ones, who fought side by side with U.S. troops against ISIS. In defending his decision, Trump insisted America has nothing at stake in Syria and can let others handle an Islamic State insurgency.

Despite the businessman-in-chief’s assertion that this role provides the United States with little benefit and a lot of human and economic costs, the reality is the opposite.

This ingratitude not only will do lasting damage to America’s reputation as a trustworthy ally, it also rejects the importance of American foreign goals more than seven decades in the making: containing an expansionist Russia; supporting allies, particularly those most likely to embrace democracy and human rights; and orienting U.S. policy away from the pre-WWII fiction that Americans at home will be safe from threats abroad — whether China, Iran or ISIS — if the U.S. would only retreat from the world.

Even one of the president’s staunchest political allies, Senate Majority Leader Mitch McConnell, felt moved to personally rebuke Trump on this count Tuesday by introducing a resolution calling on him to rescind his order to leave Syria because of how deeply it contravenes the American political inheritance that both parties have nurtured until now.

“If we Americans care at all about the post-World War II international system that has sustained an unprecedented era of peace, prosperity and technological development, we must recognize that we are its indispensable nation,” he noted ahead of introducing the resolution, which coincided with the end of a cease-fire whose expiration will likely result in more Kurds being killed. “The most important thing the Senate can do right now is speak clearly and reaffirm the core principles that unite most of us, Republicans and Democrats, about the proper role for America in Syria, the Middle East and the world.”

Despite the businessman-in-chief’s assertion that this role provides the United States with little benefit and a lot of human and economic costs, the reality is the opposite. In fact, the burdens America assumes by providing this global leadership generate a tremendous return on investment. Since the end of WWII, presidents right, left and center have understood that U.S. power and wealth can only be sustained by assuming great responsibility. As a consequence, under America’s watch, there has been no third catastrophic war, economic well-being has surged at home and abroad, and liberal democracy has spread— albeit unevenly — to places where it was once unthinkable.

There is also a case against U.S. global leadership, of course. As a superpower, America has periodically entangled itself in costly wars that have proven deeply divisive, from Korea and Vietnam to the second war with Iraq and, increasingly, the 18-year war in Afghanistan. Trump rails against “endless wars,” and sees China and Iran as taking advantage of these conflicts to undermine American power (though he has a puzzling blind spot for Vladimir Putin’s Russia).

Trump also believes the foreign policy establishment is addicted to bad deals. And, of course, some deals are bad; the Iran nuclear accord — with all its sunset clauses, allowances for Tehran to continue development of advanced centrifuges and ballistic missiles, verification inadequacies, massive sanctions relief and utter disinterest in the clerical regime’s regional expansion — was a bad deal.

But Trump sees only bad deals. He does not grasp the long-term value of the treaties responsible for both the establishment of NATO and the U.S. alliances with Japan and South Korea. American leadership depends in no small part on such sustained alliances and agreements, which signal to potential aggressors that they will face concerted opposition if they provoke a conflict. While certain allies should, as Trump demands, absolutely contribute more to the common defense, he continually fails to recognize their sacrifices, such as the loss of hundreds of NATO troops in Afghanistan.

And Trump has an equally simplistic view of U.S. military power. He insists he only wants to fight to win, then brings troops home despite military advisers constantly reminding him that victories unravel if some troops don’t stay in the field to preserve stability. Trump also seems oblivious to the role that U.S. troops play in deterring conflict, which is greatly preferable to fighting.

The result is that this president diverges from all of his predecessors since 1945 — routinely insulting allies, praising dictators and demonstrating little concern for human rights. He and his defenders seem to take pride in his combative “realism,” a school of thought in foreign policy that treats spreading American values as mostly a hindrance to the pursuit of national interests. But even President Richard Nixon and his aide Henry Kissinger, the most “realist” of American statesmen, were never this dismissive of allies, democracy and other American values. That is because they understood that our values can also serve our interests by showing our allies and partners that our success benefits them, too.

A rough balance of power between the leading countries held until aggressive dictatorships tested its limits in the years before World Wars I and II.

Before Trump, “realist” presidents — Nixon and George H. W. Bush come to mind — were cautious and deliberative, working through a consultative national security process. Neither would have been tweeters. They placed a premium on pursuing order and stability through an extensive network of alliances. Bush 1 brought together 38 other countries behind the American effort to expel Saddam Hussein from Kuwait. Such an effort would be inconceivable for Trump.

To his credit, Trump had until now avoided major debacles, such as President George W. Bush’s mismanagement of post-war Iraq or President Barack Obama’s reckless withdrawal from the country in 2011 after Bush’s “surge” of troops had stabilized the country. Yet Obama’s refusal of responsibility foreshadowed the mistakes of his successor. While focusing on Trump on Tuesday, McConnell also remarked on how “Libya and Syria both testify to the bloody results of the Obama administration’s ‘leading from behind.’” Obama was the one, after all, who inked the nuclear deal with Iran.

Somehow, Trump managed to avoid disaster for almost three years, even as he acted impulsively, ignored his advisers, proved credulous toward foreign strongmen and showed his ingratitude toward allies. But in the case of Syria, there were immediate and violent ramifications to Trump’s improvised withdrawal of U.S. troops, giving Turkey an effective green light to invade: Kurdish fighters died and tens of thousands of civilians fled; hundreds of jailed ISIS militants escaped; and one of the few remaining sources of resistance to the Russian- and Iranian-backed Syrian government evaporated.

Trump’s response to the bipartisan backlash on Syria over these predictable results has been to double down on his rejection of American intervention. He tweeted that U.S. troops were coming home because ISIS had been defeated (even though it remains a potent threat) and “we are 7,000 miles away” — an odd statement for someone who went to Lower Manhattan just days after Sept. 11.

In the first half of the 20th century, there were several great powers but no dominant one. A rough balance of power between the leading countries held until aggressive dictatorships tested its limits in the years before World Wars I and II. No single country was willing or able to prevent the onset of these twin catastrophes that almost gutted European civilization.

Will the free world fare better this time around in the absence of American leadership? When Trump leaves office, in two years or six, U.S. foreign policy may revert to its post-WWII norm. Or Republicans and Democrats may decide that America no longer has an appetite for leadership and it should continue with an isolationist stance. If so, the future may begin to look like the pre-1945 past with daunting speed.