The nationalists have gained traction for their cause in recent months by taking advantage of the government’s political weakness, forcing the governing party to take a tougher stand on the islands west of here, known as the Senkakus in Japan and the Diaoyu in China.

But the activists are also tapping into a widespread anxiety over China, which intensified two years ago during the last major flare-up over the Senkakus. China retaliated then for Japan’s arrest of a fishing captain by starving Japan of the rare earths needed for its already struggling electronics industry. That anxiety became more pronounced in recent months as China expanded its claims in the nearby South China Sea, challenging Vietnam, the Philippines and others over more than 40 islands in a vast area, and backing its statements with aggressive moves that included sending larger patrol boats to disputed waters.

There is still little appetite in pacifist Japan for a full-blown confrontation with China. But analysts say consensus is growing on the need to stand up to China as power in the region appears to slip further from economically fading Japan and the United States.

“We are all gearing up for an international tug of war in this region,” said Narushige Michishita, an expert on security issues at the National Graduate Institute for Policy Studies in Tokyo. “Whenever the distribution of power changes in a dramatic way, people start to redraw lines.”

That is precisely what is happening in the South China Sea, which has received more international attention than Japan’s territorial battles. But experts say the increasingly shrill war of words over disputed islands between Japan and its East Asian neighbors, including China and South Korea, is potentially more explosive. Unlike in the South China Sea, where the frictions center on competition for natural resources, the East Asian island disputes are more about history, rooted in lingering — and easily ignited — anger over Japan’s brutal dominance decades ago.