Between China's 20th Communist Party Congress, that began Sunday, and the next one in 2027, Japan will undertake its biggest arms buildup since World War II in a race to deter Beijing from war in East Asia, according to Japanese government officials and security analysts.

Japan identified China as its chief adversary in its 2019 defense white paper, worried that Beijing's flouting of international norms, pressure on Taiwan and rapid military modernization posed a serious security threat. That anxiety has intensified since Russia invaded Ukraine, weakening Japanese public opposition to rearming, security experts say.

The government "has the wind at its back and will use that to do whatever it can," said Takashi Kawakami, a professor at Takushoku University in Tokyo. By pointing to 2027 as the moment when East Asia's power balance may tip in China's favor, Japan's government can rally support for greater defense spending, he added.