Upon graduating from medical school, physicians typically take the Hippocratic Oath. Though the oath doesn’t actually contain the phrase “first do no harm” that is so prevalently linked to it, the underlying premise is there. Japanese Prime Minister Shinzo Abe would do well to adopt such a code for his foreign policy.

Abe’s needless and shameless series of self-inflicted diplomatic wounds have hindered his ability to implement long-overdue Japanese defense reforms, which, in turn, risks U.S. security objectives in Asia.

Abe’s latest diplomatic gaffe was this week’s revelation that in April the prime minister sent a message of support to a ceremony honoring Japan’s Class-A and other war criminals. Abe’s letter praised those executed by the Allied powers as having “staked their souls to become the foundation of their nation.”

The annual event takes place at a memorial statue built in 1994 to restore the honor of war criminals, describing their punishment by the Allied powers as “a harsh and retaliatory trial never before seen in the world.” Included in the list of 1,180 war criminals at the statue are the 14 Class-A war criminals who are enshrined at the controversial Yasukuni Shrine.

After World War II, the International Military Tribunal for the Far East in Tokyo tried 28 Class-A war criminals for crimes against peace by conspiring to wage wars of aggression in violation of international law. In addition, Class-B and Class-C criminals were convicted of conventional war crimes and crimes against humanity.

As part of the 1951 Treaty of Peace with Japan, “Japan accept[ed] the judgments of the International Military Tribunal for the Far East and of other Allied War Crimes Courts both within and outside Japan.” Abe’s chief cabinet secretary Yoshihide Suga affirmed on August 27 that Japan accepted the judgments of the tribunal. Suga sought to downplay the controversy by stating that Abe wrote not in his capacity as prime minister but as the leader of the ruling party.

Abe’s message, like his December 2013 visit to Yasukuni Shrine, reflects a tin-eared and ham-fisted diplomatic approach toward resolving historical issues that needlessly exacerbates tensions with South Korea and the United States. Although Abe often tempers his inflammatory gestures with pledges to maintain Japan’s quest for peace, the resulting controversy engulfs any ongoing efforts at reconciliation with Seoul.

For its part, South Korean policy toward Japan has devolved to emotional nationalism with every present-day issue interpreted through the lens of history. Doing so has led Seoul to reject a military intelligence-sharing agreement that would improve South Korean defenses and see greater commonality with authoritarian China—which fought against South Korea in the 1950s—than with fellow democracy Japan.

Abe’s latest egregious faux pas will further hinder efforts for Japan to implement collective self-defense, a much-needed reform to have Tokyo assume greater responsibility for its security and more fully participate in international peacekeeping operations. Revisionist historical comments by Abe and other Japanese politicians fuel South Korean suspicion toward Japan and misperceptions that collective self-defense is a prelude to another Japanese invasion of the Korean Peninsula.

If Tokyo wants to move beyond the history issues in order to fulfill its own policy objectives and play a more effective regional and global role, it must make a concerted, systematic effort to alleviate its neighbors’ concerns over historical issues by forthrightly and consistently repudiating its past and denying those who deny the past.