After 17 years of tense delay, local Japanese authorities will allow the U.S. military to relocate an air base on the strategically significant island of Okinawa. Think of it as a triumph of democratic realism in the face of renewed regional threats.

Okinawa hosts about half of the 50,000 U.S. troops stationed in Japan, with some 4,000 Marines based at Futenma Air Station, built in 1945 and now surrounded by a city of nearly 100,000. Locals have long complained of noise, pollution and safety risks relating to Futenma. In 1996—after three U.S. Marines raped a local schoolgirl—Washington and Tokyo agreed to relocate the base to a less-populated site on Okinawa's coast. Yet that didn't satisfy various anti-American activists and environmentalists who wanted the base moved out of Okinawa—or Japan.

Okinawa Gov. Hirokazu Nakaima Associated Press

By 2009, opponents of the relocation plan included Japan's then-prime minister, Yukio Hatoyama, who sought to banish Futenma as part of a broader foreign-policy tilt toward an imagined "East Asian Community" that excluded the United States. This idea went nowhere, and 10 months later Mr. Hatoyama was out of office, with his replacements eager to highlight the importance of the U.S. alliance. Relocation plans nonetheless remained stalled at the local level until last week.

Okinawa Governor Hirokazu Nakaima blessed the relocation last Friday after accepting Prime Minister Shinzo Abe's offer of at least 300 billion yen, or $2.9 billion, in development aid every year until 2021. The governor promises environmental protection around the new base and hopes that Futenma will be able to halt operations within five years. Closing Futenma allows the U.S. to proceed with broader plans to move about 8,000 Marines out of Okinawa to bases in Hawaii, Guam and Australia.

Along with Mr. Abe, credit for the Okinawa breakthrough goes to China's saber-rattling, which is causing nervous officials across Asia to strengthen defense ties with the U.S. "Regardless of the sentiment of Okinawan people on military presence, the tension of international situations has been increasing in recent days, and Okinawa must play a certain role," Mr. Nakaima said on Friday. Okinawa prefecture includes the Senkaku Islands, which Beijing claims as Chinese territory covered by a self-declared Chinese air-defense identification zone. In 2012 Tokyo scrambled fighter jets a record 306 times due to Chinese incursions in and around Japanese territory.

U.S. officials say that progress on Okinawa bodes well for U.S. military negotiations with the Philippines, South Korea, Vietnam and other states in China's shadow. Let's hope that's right. Good relations among these states and with Washington will determine whether Beijing's aggressive behavior will be deterred.

As he enters his second year in office, Shinzo Abe has an opportunity to put Japan at the heart of a community of East Asian democracies. His visit last week to the Yasukuni shrine didn't help, but we're hoping the prime minister can orient Japan's foreign policy toward a better future, not the compromised past.