Beijing—There are many obscure tourist sites in Beijing. One missed by many foreigners is the Chinese People’s Anti-Japanese War Memorial Hall. The museum illustrates why China, America’s most fearsome potential competitor, and Japan, Washington’s most important Asian ally, often are at odds. The two are a conflict waiting to happen, which could draw the U.S. into war with a nuclear power.

Yesterday Chinese President Xi Jinping presided over a World War II victory parade in Beijing. The People’s Republic of China didn’t even exist 70 years ago when Tokyo surrendered. Most of the fighting against Japan was conducted by Chiang Kai-shek’s Nationalist government. But the PRC filled Tiananmen Square with military personnel and hardware to celebrate “its” victory over China’s historic enemy.