When Russia invaded Ukraine in 2022, for example, Washington responded by leading an international coalition to support Kyiv and help it resist and survive. Through the delivery of relatively modest amounts of military and economic aid to a friend in desperate need, Russian aggression was checked and NATO gained new members and a new sense of purpose—a rare popular, bipartisan foreign policy achievement.

But during 2023, Ukrainian forward progress stalled and Trump regained his hold on the Republican party. He turned support for Kyiv into a partisan wedge issue, demanding that his followers accommodate Moscow and sell out America’s partner. The more his political fortunes revived, the more his attempt to set a new party line gained traction. And now, thanks to the opposition of his minions, aid is about to be cut off.

At this point, therefore, Ukraine is facing its “Battle of Britain” moment—a period in which it must find a way to survive with limited American involvement even as it endures brutal attack, just like the United Kingdom did in 1940. Kyiv and its remaining friends need to stay in the fight, crouching and counterpunching and hanging on until the American presidential election in November. Trump and his isolationism will be on the ballot, and the result will send the world in one of two dramatically different directions.

If Trump loses, more active American global engagement will once again become possible. Further aid would be sent to Ukraine, Putin’s hopes of outlasting his enemies would be dashed, and the liberal international order would get a new lease on life.

If Trump wins, however, all bets are off, and not just for Ukraine. It is likely that in a second term, an angry and empowered Trump would move more quickly, forcefully, and effectively to achieve his goals, among which be a more isolationist foreign policy. Self-interested transactionalism would be everything; gone would be any sense of teamwork or partnership with others on equal terms in collective endeavors.

Trump is better at breaking things than creating them, and he has no plausible vision of international order to put in place of the existing system. Nor does he want real crises, only the appearance of them. So, his foreign policy is likely to produce decline and entropy, rot rather than revolution. The webs of benign international enmeshment will continue to fray, and the trust that underlies a sense of global community will continue to erode. “There is a great deal of ruin in a nation,” Adam Smith once said, and the same is true of an international order, especially one as comprehensive and deeply rooted as the Pax Americana has been to date. It is not at all clear what a post-American world would look like.

But astonishingly, we may start to find out soon enough.

About the Author: Gideon Rose, Former Editor of Foreign Affairs 

Gideon Rose is adjunct senior fellow at the Council on Foreign Relations (CFR). Previously, he was editor of Foreign Affairs from 2010 to 2021, prior to which he was managing editor from 2000 to 2010. He has also served as associate director for Near East and South Asian affairs on the staff of the National Security Council and deputy director of national security studies at CFR, and has taught American foreign policy at Princeton and Columbia. He is the author of How Wars End (Simon & Schuster, October 2010).