A decade ago, Japan sent troops to Iraq. The Japanese Iraq Reconstruction and Support Group was Tokyo’s first multilateral military mission outside of U.N. peacekeeping operations.

To observers at the time, it felt like a watershed moment for a country that, since World War II, has been reluctant to use force in pursuit of its foreign policy. The deployment paid off for Japanese-U.S. relations, but at great risk to Tokyo and to the troops on the ground.

Ten years on, Tokyo should have learned from its experiences in Iraq. But it hasn’t. With only one minor caveat, the Japanese military is as hamstrung as ever.

From the outset, the Iraq deployment seemed to require everything that the Japanese military couldn’t do. Combat? Off the table—Japan declines to use force except in cases of national self-defense.

That policy derives from Article 9 of the postwar constitution, which asserts that “the Japanese people forever renounce war” and bans air, sea and land forces. By any reading, Japan’s military itself should be unconstitutional.

Tokyo has managed to skirt this prohibition by calling its military the “Self-Defense Forces.” But semantics cannot hide the fact that Japan maintains the very army, navy and air force that its constitution forbids.

Still, these forces rarely left Japan’s borders even as the country quickly rose to become one of the world’s leading powers. Pacifist Tokyo managed to contribute indirectly to world security by sending money instead of troops. Japan contributed $13 billion to the cost of the U.S.-led war with Iraq in January and February 1991.

After that conflict, and under much criticism, Prime Minister Toshiki Kaifu stressed that this s0-called “checkbook diplomacy” was inadequate. “I think it is widely understood we have to make personnel contributions as well as financial ones,” Kaifu said.

Shamed by the experience, a committee of lawmakers under Ichiro Ozawa led a transformation of the Japanese military from a Cold War defensive force to an army of peacekeepers.

By connecting international security efforts to national self-defense, Japanese policymakers were able to begin sending the military on U.N. peacekeeping missions. But the Iraq war wasn’t a peacekeeping operation.

Prime Minister Jun’ichiro Koizumi had pledged Japan’s support for U.S. president George W. Bush’s “war on terror” as early as February 2002, according to the Mainichi Shimbun newspaper. The Bush administration maintained that invading Iraq was a necessary part of the international campaign against Islamic terrorists.

Koizumi dutifully promised Bush that Japan would back America in Iraq, knowing full well that doing so would hurt his image among the Japanese public. The U.S.-led coalition attacked Iraq in March 2003. The prime minister voiced his strong support … and his disapproval rating quickly leaped to 49 percent.

Koizumi was acutely aware of Japan’s need to show solidarity with the U.S., which bases significant forces in Japan and helps protect the island nation—in effect, allowing Tokyo to maintain its official pacifism without actually exposing itself to attack.

At the May 2003 U.S.-Japan summit, Koizumi assured Bush that “Japan wished to make a contribution [to the reconstruction of Iraq] commensurate with its national power and standing.”

The first Japanese troops would arrive in Iraq eight months later.