The “Free World,” as a term for the global community of free-market democracies, owes its origins to Frank Capra’s 1943 propaganda film, Why We Fight, which laid out the case for war with fascist Germany and an imperial Japan, and for forming an alliance with the decidedly unfree and undemocratic Soviet Union. The film does not frame the Second World War as yet another amoral test of strength between Europe’s great powers and their colonies, but as a global struggle of ideologies, and one that threatened to snuff out the freedoms the United States held most dear.

The term “Leader of the Free World,” however, came into usage during the Cold War, a time of relative peace between great powers. It referred exclusively to the U.S. president, since the U.S. was the undisputed leader of the Western coalition. When the Soviet premier sought to negotiate with the West, he negotiated with the U.S. president. Some of these summits were celebrated successes, like the first Strategic Arms Limitation Talks (SALT I), while others, like the much-anticipated Vienna Summit between President John F. Kennedy and Soviet Premier Nikita Khrushchev, were dismal failures. But even after these failures, both sides continued to return to the negotiating table because leaders on both sides knew that they were playing only a few rounds of a much longer, iterated game.

To be sure, the Soviet Union and the U.S. distrusted each other, and both sides gave the other side reasons to do so. But both countries were also constrained from flagrantly violating their commitments, and the commitments made by their predecessors, by the knowledge that their successor would have to account for those betrayals in the next round of negotiations, be they with this particular rival or another. Ultimately, even through the darkest moments of the Cold War, like the Cuban Missile Crisis, the lines of communication stayed open, and a minimum of trust was preserved. Our ability and willingness to offer concessions—and to negotiate in good faith even with those who wished us harm—prevented global catastrophe and ultimately allowed the liberal West to emerge victorious.

By reneging on the Joint Comprehensive Plan of Action (JCPoA), the U.S. breaks its word, sully its honor, and cheapens its other commitments. Why should North Korea now agree to concessions, when it knows that the U.S. government will violate its commitments at the first convenient moment? Why should Iran ever return to the table to discuss nuclear weapons, ballistic missiles, support for terrorism, or anything else, when it knows that the U.S. cannot be trusted? Wars occur when countries stop talking, and countries stop talking when they feel they have nothing to gain from negotiation, or that the accords they reach will not be honored. By so flagrantly breaking the word of the U.S., President Donald Trump has taken a hatchet to our diplomatic credibility, making war in the coming years more likely.

Our best hope to contain the damage is for European leaders to rise to the occasion. British Prime Minister Theresa May, French President Emmanuel Macron, and German Chancellor Angela Merkel, as well as other NATO and EU leaders, must make a concerted effort to demonstrate that current American policy is aberrant, and not the “new normal” of Western values and conduct. They must adhere to the agreement and resist pressure from Washington to impose new sanctions on Tehran, as long as it abides by the original deal, while also impressing upon Iranian President Hassan Rouhani the importance of remaining in compliance with it, even in the face of American provocations. In short, European leaders must jointly take up the mantle of “Leader of the Free World.” In Europe, it is harder to forget that diplomacy is the only reason that WWII has remained the high-water mark of human violence for so long. Whether this changing of the guard is a temporary stewardship, or an end of the American Era altogether, will be up to us.

The views expressed in this article are the author’s own.

Image: President Donald Trump holds up a memorandum that reinstates sanctions on Iran after he announced his decision to withdraw the U.S. from the 2015 Iran nuclear deal on May 8. Photo by Chip Somodevilla/Getty Images