Japan's Prime Minister Shinzo Abe has secured a rare opportunity for constitutional reform following the July 10 election for the upper house of the Diet, or parliament. His ruling coalition now has a supermajority in both houses. Yet he is right to tread cautiously on constitutional change. Since many Japanese remain wary of amending a constitution that is widely seen as having brought a long period of peace, the government would be hard pressed to win a national referendum on constitutional change -- even if any proposed amendment passed both houses of the Diet with the required two-thirds majority.

If there is one factor that could help ease grassroots concerns and facilitate constitutional reform, it is American support for the process. This would help blunt criticism from Japan's powerful pacifist constituency as well as from China, which equates any potential constitutional change with Japan's remilitarization -- even as Beijing frenetically builds up its own military might.

U.S. security interests would be better served by a more confident and secure Japan that assumes greater responsibility for its own defense and regional security. National security reforms in Japan are tied to constitutional reforms. Together, they would help strengthen the central goal of the U.S strategy for the Asia-Pacific -- a stable balance of power.

Japan has been a model U.S. ally, hosting a large U.S. troop presence and contributing billions of dollars to support the costs of stationing those forces on its soil. The U.S. has said this assistance is "by far the most generous host-nation support" provided by any of the 27 allies with which Washington has defense treaties. Japan's financial support is so significant that it is approximately equivalent to the U.S. annual budget for maintaining domestic military bases -- a fact that Republican presidential nominee Donald Trump seemed unaware of when he said Tokyo should pay more.

Because of Japanese generosity, it is cheaper for the U.S. to have its troops stationed in Japan than back home. In fact, Tokyo recently agreed to marginally increase its host-nation support after initially seeking to cut its contribution to help reduce Japan's massive public debt.

More important, the alliance with Japan remains central to the U.S. role in Asia, including maintaining a forward military presence. However, the U.S. faces major new challenges in the region due to the rise of an increasingly assertive China - best symbolized by Beijing's rejection of the July 12 international tribunal ruling that knocked the bottom out of its expansive sovereignty claims in the South China Sea. China's creeping aggression in Asia reflects a "might makes right" strategy designed to extend Chinese control to strategic areas and resources -- from the East China Sea to the Himalayas.

In this light, peace in Asia demands a proactive Japan. The issue Japan faces is not whether it should remain pacifist, since it is unlikely to discard pacifism, but whether it can afford to stay passive in regional and international affairs. A Japan that is better able to defend itself and to cooperate with friendly Indo-Pacific countries to forestall a destabilizing power disequilibrium in Asia would truly become a "proactive contributor to peace" -- a concept popularized by the Abe government.

A weaker defense alliance

If Tokyo, however, fails to carry out further reforms of its postwar institutions and policies to meet the new challenges in Asia, it could not only weaken its own security but also the role of the U.S.-Japan strategic alliance.

By drafting and imposing a constitution after World War II, the U.S. created the problem that Japan now confronts -- how to cast off the constitutional albatross. The U.S. must seek to be part of the solution so that Japan, in keeping with American interests, plays a proactive role in Asian affairs and does more for its own defense. Japan can play this role within the framework of its longstanding security treaty with Washington.

It has been largely forgotten that Supreme Allied Commander Douglas MacArthur made his occupation staff hastily write the Japanese constitution in just one week so that it would be ready to coincide with the U.S. national holiday celebrating Abraham Lincoln's birthday on Feb. 12, 1946. However, it did not come into force until May 1947. No national constitution in the world goes so far as Japan's in barring the acquisition of the means of war or to renounce "the threat or use of force as a means of settling international disputes." A defeated Germany escaped Japan-like constitutional fetters because by the time its constitution, or Basic Law, was drafted in 1949, the Cold War was in full swing.

It did not take long for the U.S. to realize that it went too far in defanging Japan when it disbanded its military and imposed the world's first pacifist constitution. After the Korean War, through a major legal reinterpretation of the constitution it had imposed, the U.S. encouraged Japan to reconstitute its military as "Self-Defense Forces" to make the country the lynchpin of its Asian strategy.

The Japanese constitution suffers from inherent flaws. For example, it defines no head of state, having stripped the emperor, then Hirohito, of all but symbolic power. Article 1 defines the emperor's position as "the symbol of the state and of the unity of the people," while Article 3 declares he "shall have no governmental powers, nor shall he assume nor be granted such powers."

This was deliberate. The U.S. wanted to have the emperor merely serve as the symbol of Japan so that Washington could use him to win public support for the U.S. occupation between 1945 and 1952, while denying him powers to oppose it. Likewise, the force-renouncing Article 9 was designed to keep Japan as an U.S. client state, while depriving it of the ability to ever mount another Pearl Harbor-style attack against the U.S. But today, U.S. security interests would be better served by a militarily stronger Japan.

Another anomaly is the absence of constitutional protection for the Japan Self-Defense Forces, 62 years after they were established, despite popular support for the military. By renouncing "war as a sovereign right of the nation and the threat or use of force as a means of settling international disputes," the constitution has imposed an impractical fetter from which Japan will have to break free to defend itself from any aggression, as Abe has said.

Contradictions

In truth, Japanese pacifism has been made possible not so much by the constitution as by the fact that Japan is under U.S. security protection. Pacifism, however, has coexisted with contradictory trends. For example, Japan has denounced nuclear weapons and consistently called for a world without them, yet welcomed the nuclear umbrella provided to it by the U.S. Japan has kept its military forces out of combat but has endorsed U.S. military interventions around the world, including the 2003 invasion of Iraq and the 2011 regime change in Libya.

But Japan's constitutional fundamentalists regard the constitution as sacrosanct, as if it were religious scripture, and oppose any change, even though the U.S. has ratified six amendments to its own constitution since it drafted the Japanese charter. At the other end of the spectrum are Japanese who seek a new constitution. They want Asia's oldest liberal democracy and one that has not fired a single shot since World War II to frame a new constitution anchored in its own values and traditions.

By placing a high bar to the enactment of any amendment, the Japanese constitution is among the hardest in the world to revise. Just 35% of Japanese support constitutional revision, according to a poll conducted by the Yomiuri Shimbun.

Against this background, only open U.S. support for constitutional reform can make a meaningful difference. It will allay public concerns among the Japanese, with only 23% wanting their country to play a more active role in regional affairs, according to a 2015 survey by the Pew Research Center. Another survey in 2014 revealed that just 15% of Japanese, compared with almost 75% of Chinese, were willing to defend their country -- the lowest figure in the world.

Unlike China, Japan is not a revisionist power. Rather, its strategic priorities converge with U.S. regional goals, including maintaining the present Asian political and maritime order to ensure a regional power equilibrium and freedom of navigation in the South China Sea. The U.S., in its own interest, should back constitutional reform in Japan, which has not sent a single soldier into combat since 1945 -- a record of pacifism surpassing even that of Germany.

Brahma Chellaney is a geostrategist and author of nine books, including "Water, Peace, and War" (Rowman & Littlefield; he is currently a professor of strategic studies at the Center for Policy Research in New Delhi and a Richard von Weizsacker Fellow at the Robert Bosch Academy in Berlin.)