All eyes were on Beijing Thursday as it commenced commemoration activities to mark the end of World War II and the victory of Chinese People’s War of Resistance Against Japanese Aggression.

Yet you may be wondering why Sept. 3 is China’s V-Day, when Japan announced surrender on Aug. 15, those 70 years ago.

Japanese Emperor Hirohito announced his country’s acceptance of the terms of the Potsdam Declaration, and its unconditional surrender, on August 15, 1945. However, without formally signing the terms of surrender, it didn’t have any legal standing.

That came about on Sept. 2, when representatives from Japan, China, and eight other Allied powers signed on the Japanese instrument of surrender on the deck of the USS Missouri in Tokyo Bay.

But it was the next day that was symbolically significant to China. On Sept. 3, the Japanese army in China formally surrendered to the Chinese government, resulting in nationwide celebrations.

Considered the first victory over a foreign invasion in Chinese modern history, Sept. 3 was chosen as the official victory day.

After the founding of People’s Republic of China in 1949, the day was reset to Aug. 15, but switched back two years later.

In 2014, China’s top legislative body ratified Sept. 3 as the “Victory Day of the Chinese People’s War of Resistance Against Japanese Aggression.”