When I first visited North Korea in 1992, I discovered that officials there and in South Korea shared at least one opinion: they hated the Japanese. Indeed, one of my hosts in Pyongyang suggested that his nation and the United States work together against Tokyo, though to do what he did not specify.

Little has changed in this regard over the years. Generational change should have relaxed the Republic of Korea’s attitude toward Japan, but attacks on Tokyo’s role in World War II continue. South Koreans seem fixated on Japanese brutality when the peninsula was an imperial colony. Japanese appear tired of being badgered to apologize for the conduct of a previous generation and activity which they claim was not as bad as charged. The controversy recently flared as South Koreans who were coerced to labor for Japanese arms makers and act as “comfort women” for Japanese soldiers sued for compensation, leading to court judgments which the Japanese government contends violate the legal and political settlement which accompanied the normalization of relations in 1965 as well as a separate 2015 pact.

South Korea threatened to seize the property of Japanese companies which refused to pay. Tokyo imposed trade sanctions on the South. Seoul suspended intelligence-sharing with Japan, leading to U.S. protests. The South resumed bilateral contact but asserted its right to again penalize Japan. American policymakers urged both sides to find a compromise, without notable success. Thus have two democratic, market-oriented U.S. allies expended more effort attacking each other than cooperating in response to increasingly aggressive Chinese behavior.

On Monday South Korean President Moon Jae-in publicly reaffirmed his willingness to meet with his Japanese counterpart, Prime Minister Yoshihide Suga. Moon stated that “I am confident that if we put our heads together in the spirit of trying to understand each other’s perspectives, we will also be able to wisely resolve issues of the past.”

Indeed, intellectually the solution seems simple. Moon noted how issues of past and future “intermingled with each other,” which “has impeded forward-looking development.” He told Tokyo: “It is by no means shameful to learn a lesson from past wrongs, but it is rather a way to gain respect from the international community.”

There is much to learn from the past, especially from multiple wars in Asia and the Pacific. Alas, the problem is not misunderstanding the other side. It is refusing to compromise on an issue that is both highly emotional and ferociously political. Finding common ground would please Washington, but that matters little with a South Korean presidential election barely a year away and Japanese parliamentary elections possible before that. Taking the most outrageous and extreme position energizes partisans and wins votes.

The issue’s roots go back more than a century. With its defeat of China in 1895, Imperial Japan gained effective control over the Kingdom of Korea, which had been a vassal state of Beijing. Fifteen years later Tokyo annexed the peninsula, which then suffered under harsh colonial rule during which Koreans were even forced to change their names and religion. Mistreatment increased during World War II as Imperial Japanese government forces waged war on China, throughout Southeast Asia and the Pacific, and against America.

Tokyo’s defeat left the peninsula under U.S. and Soviet occupation. Yet even then many leading Japanese exhibited no remorse over the treatment of Korea. Convinced in both their ethnic superiority and moral righteousness, they lectured Koreans on how lucky the latter had been to have benefited from Tokyo’s tutelage. This strategy was not designed to ease bitter historic antagonisms.

Nevertheless, the Cold War created pressure for accommodation, and in 1965 the two governments agreed to establish diplomatic relations. Tokyo provided development aid—about $8 billion in today’s dollars—which was widely viewed as unofficial reparations, a payment intended to assuage anger and informally settle financial claims. However, relations remained fraught: territorial disputes, angry memories, and periodic insults divided the two U.S. allies. Even a 2015 agreement intended to settle the “comfort women” issue fell apart.

After long blocking lawsuits against Japanese companies, the South Korean Constitutional Court changed course. Then the Seoul government conveniently claimed to be powerless while hiding behind a judicial ruling which it favored. Yet Tokyo also had little credibility: Japanese officials spent decades refusing to forthrightly acknowledge the grotesque misbehavior of the imperial regime, which so stained their nation’s reputation, and the profound pain this history continued to cause surviving victims.

Washington could do little over the years other than dolefully call on its allies to be nice to each another. Trump administration officials did their best to run from the room whenever historical issues arose, at least until South Korea announced that it would withdraw from the General Security of Military Information Agreement (GSOMIA), which provided for intelligence sharing. Then the United States pushed Seoul to return, which the latter reluctantly did, while urging Japan to reciprocate, which the latter refused to do.

Around the same time Moon’s government initiated military exercises on the disputed Dokdo islands (known as the Takeshima islands by Japan and Liancourt Rocks by the United States). This naturally triggered caterwauling in Tokyo and Washington’s assessment that the ROK’s behavior was “not productive.” Neither of which troubled Seoul.

Now there is a new government in Tokyo, which creates an opportunity for a reset. Moon argued: “There has never been a time when cooperation among neighboring countries has been as vital as it is now.” That is true but, in the highly politicized bilateral political environment, unfortunately irrelevant. Neither personality nor politics inclines Suga to be innovative or courageous. Whatever honeymoon he had when succeeding the ailing Shinzo Abe has dissipated. His weakened political position makes him vulnerable to challenges within his own party, so he is unlikely to take political risks to improve mutual understanding.

This ugly international fight led to repeated calls for Washington to do something, but what is unclear. First, the United States is most concerned about its own interests. That is why the Trump administration acted only when intelligence cooperation was threatened. Explained an anonymous State Department official: “the most recent action on the part of Seoul directly affects U.S. security interests. This is something we can’t sit quiet for.”

Second, there is no easy way to repair the break. However arbitrary and arcane the dispute might seem to Americans, it runs deep in both South Korea and Japan. National pride is at stake and upon it elections could be decided. In the face of such stakes, pleas for sweet reasonableness from Washington go only so far—which isn’t far.

Indeed, the more Washington appears to be invested in its relationship with both governments, paradoxically the less its ability to influence their behavior. The presumption that America will protect them from outside threats reduces their perceived cost of irresponsible behavior toward each other.

In contrast, rising fear of China and doubts about Washington’s future commitment have led them and other countries to begin hedging. For instance, Tokyo is doing more militarily, slowly but surely. The Philippines has grown substantially friendlier toward the idea of a more active Japanese military role in East Asian waters. Grandstanding looks less attractive with a potential regional hegemon increasingly active nearby.

The Biden administration should work to bring together Seoul and Tokyo. Whatever their historical differences, neither government threatens the other today. Both have much more to fear from North Korea and China than each other, and therefore should cooperate on a variety of security issues.

However, words are not enough. The administration should use its ongoing posture review to warn both governments that at a time of budget stringency neither U.S. commitments nor deployments are fixed. And an unwillingness to do more to defend themselves will reduce Washington’s enthusiasm for coming to their defense, especially of more peripheral interests, such as contested islands. The China challenge is serious; Japanese and South Korean behavior is not.

President Moon’s offer may not quite be an olive branch—perhaps more an olive twig or two. Still, his comments warrant a response from Tokyo. With an assist from Washington, perhaps America’s allies can initiate their own peace process. Success would be a significant step forward, improving regional stability and security.