TOKYO >> Japan stepped up its alarm over China’s assertiveness in the region, its growing military ties to Russia and its claims on Taiwan in an annual defense paper released Friday that is the first under Tokyo’s new security strategy calling for a major military buildup.

The current security environment is the worst since the end of World War II, according to the 2023 edition of Japan’s defense white paper approved by Prime Minister Fumio Kishida’s Cabinet. It is the first under the National Security Strategy the government adopted in December, stating the need to bolster strike capability with long-range missiles like Tomahawks, a controversial plan seen as a break from Japan’s self-defense-only postwar principle.

China, Russia and North Korea contribute to “the most severe and complex security environment since the end of World War II,” according to the 510-page report. It says China’s external stance and military activities have become a “serious concern for Japan and the international community and present an unprecedented and the greatest strategic challenge.”

Russia and China have also stepped up strategic ties, the report said, noting repeated joint bomber flights and joint navigations of Chinese and Russian warships are “clearly intended for demonstration of force against Japan and of grave concern” to security of Japan and the region.

The report noted China and Russia conducted at least five joint bomber flights since 2019, including one in November last year.

The report noted an outlook for China to possess 1,500 nuclear warheads by 2035 and its increasing military superiority over Taiwan, which raises regional tensions and is a security threat, especially to Japan’s southwestern islands including Okinawa.

Many residents there have bitter memories of the Battle of Okinawa, in which Japan’s wartime military essentially sacrificed the local population in an attempt to delay a U.S. landing on the main Japanese islands. Many Okinawans worry they would be the first to suffer again, in the event of a Taiwan emergency.

While Okinawan Gov. Denny Tamaki has called for U.S. bases there to be reduced and for greater effort in diplomacy and dialogue with Beijing, the central government has been reinforcing the defenses of the remote southwestern islands, including Ishigaki and Yonaguni, where new bases for missile defense have been installed.

Earlier this week, Chief Cabinet Secretary Hirokazu Matsuno visited Ishigaki and acknowledged the challenges of evacuating residents from remote islands, and pledged to give firm support. Ishigaki Mayor Yoshitaka Nakayama asked for airport and port facilities to be reinforced and for underground shelters to be built for residents in case of a Taiwan emergency.

China claims self-governing Taiwan as its own territory, to be annexed by force if necessary.

Chinese President Xi Jinping, who in 2017 set a goal of building “world-class military” by mid-21st century, may move the target forward, the report said, noting his call for a rapid advancement of the People’s Liberation Army to world-class in his speech at the Communist Party congress in October.

North Korea is rapidly progressing in its nuclear and missile development and poses a graver, more imminent threat to Japan than ever before,” the report said. The North has test-fired around 100 missiles since the start of 2022, including ICBMs, and the report noted the country is now believed to have an ability to conduct nuclear attacks on Japan and continental United States.

The report comes seven months after Kishida’s government adopted new national security and defense strategies that stated a decision to bolster Japan’s military capability and double defense budget by 2027 to 43 trillion yen ($310 billion).

Questions have been raised about whether the ambitious expansion of military capability and funding for it is feasible in a country that has a rapidly aging and shrinking population.

A government-commissioned panel recently adopted a package of measures, including scholarships, extension of retirement age, hiring retirees, improving workplace environments and tackling harassment.