The United States and Japan are parties to a defense and security alliance established by a Treaty of Mutual Cooperation and Security signed on September 8, 1951, and revised on January 19, 1960. According to Article 5 of that Treaty, U.S. and Japan are bound to respond to an armed attack on either country.

Most recent updates stipulate that the treaty covers Japan’s administered and China claimed Senkaku/Diaoyu islands. Cyberattacks are also covered, along with electronic and space warfare.

The U.S.-Japan alliance is now considered the pillar of the Indo-Pacific security designed to counter challenges from China and North Korea.

To accomplish that mission, Japan has granted the U.S. the use of land, air and naval facilities, with more than 100 American military installations in Japan operated by an estimated 60,000 of active-duty personnel.

All that captures the meaning of former Senator Mike Mansfield’s famous statement that the U.S.-Japan alliance “is the most important bilateral relationship in the world, bar none.” Mansfield was also the longest serving U.S. ambassador to Japan (from 1977 to 1988) who emphasized that the alliance provided the stability, security and free trade to the developing East Asian economies during the tense period of Cold War years.

Love thy neighbor

That mission continues, with particular attention to U.S. guarantees of the freedom of navigation in the air and sea lanes of East and South China Seas that handle each year an estimated one-fourth ($7.4 trillion) of world trade.

Japan is, therefore, a de facto party to all of this by virtue of its treaty alliance with the United States. The corollary is that the U.S.-China agreement to pursue strategic stability also covers the relationship between the two large Asian neighbors.

This discussion was necessary to clarify the significance of China and Japan inability to come to terms about their legacy problems, and the way to go forward, while continuing to conduct a booming and nearly balanced bilateral trade.

During the 14 years (1931-1945) of resisting the Japanese aggression, 35 million Chinese were killed or wounded. Japan’s horrific war crimes were committed in Nanjing where an estimated 300,000 civilians and unarmed soldiers lost their lives.

Speaking last August at an event commemorating the war dead, Japan’s emperor expressed “a sense of deep remorse,” but no similar statement was heard from the prime minister.

China and Japan never even tried to reconcile. Old enmities continued to simmer and erupted as China’s strong economic growth led to its assertive power projections on the world scale.

Japan responded by denouncing growing regional security threats – despite America’s formidable military presence – complaining about the straitjacket of its peaceful constitution, while building up its own Self Defense Forces and expanding the defense arsenal.

Follow Shinzo Abe’s advice

The latest and the most flammable incident came with Japan’s Prime Minister Sanae Takaichi statement in November 2025 about Taiwan, a self-governed island China claims as its province and an internal matter off limits to foreign interference. She repeated what her mentor and former Prime Minister Shinzo Abe said that an attack or blockade of Taiwan by China would create a “survival threatening situation” for Japan, triggering a military intervention. Presumably, the assumption here was that the U.S. would be involved and Japan would have to join the fighting under provisions of the treaty alliance.

Predictably, that infuriated Beijing. Takaichi refused to retract the statement, but she apparently said that she would no longer comment on hypothetical events.

What followed is the usual visit to China of a large Japanese business delegation on September 27, 2026, trying to calm things down and restore normal trade relations.

Because the trade business looks good. Bilateral transactions in the first eight months of this year soared at an annual rate of 18 percent to $243.4 billion, China’s purchases of Japanese goods surged 28 percent and Japanese imports from China rose a relatively modest 8 percent.

China and Japan need a thorough and constructive dialogue in the context of the U.S.-China work on strategic stability.

There will soon be two opportunities for Beijing and Tokyo to engage at the highest level – hopefully with the assistance of the United States. The first occasion to do that will be at the APEC (Asia Pacific Economic Cooperation) summit in Shenzhen, China, on November 18-19, 2026. And then there will be the G20 summit in Miami, FL on December 14-15, 2026.

Recent Japan public opinion polls show 69 percent of respondents believed that efforts to improve relations with China were necessary. And a Nikkei survey of Japanese business leaders indicated that 67 percent thought that worsening relations had negative effect on their business in China, but 86 percent did not plan to change their business activities in China.

For Japan, things should be clear. Its sluggish economic growth of 0.8 percent in the first half of this year was entirely driven by net exports growth of 0.6 percent. And that growth did not come from a 3.2 percent decline of Japan’s sales to the U.S. or from the puny 3 percent increase in sales to the European Union. Japan’s export growth came mainly from a blistering 28 percent increase in business transactions with China.

Takaichi should follow the wise advice of her mentor and predecessor Shinzo Abe who said during his press conference on December 16, 2012, that "China is an indispensable country for the Japanese economy to keep growing. We need to use some wisdom so that political problems will not develop and affect economic issues."