China’s naval and air forces began what observers described as unusually large exercises in the Western Pacific and South China Sea this weekend, including H-6K bombers, Tu-154 reconnaissance planes, Yun-8 transport planes, and Su-30 and Su-35 fighters.

The Su-35 is a highly advanced fourth-generation fighter that has only been sent to the South China Sea for drills on one previous occasion. The H-6K bomber is capable of carrying long-range cruise missiles that can threaten ships or ground targets, possibly with nuclear warheads.

The combat drills passed over the Miyako Strait near Okinawa, which lies between Japan’s southern islands. The strait also happens to be located between Japan, Taiwan, and the Senkaku Islands, where Japan, Taiwan, and China all have conflicting territorial claims.

The Chinese military described the exercise as its “best preparation for war,” according to the South China Morning Post (SCMP).

“Air force exercises are rehearsals for future wars and are the most direct preparation for combat,” the Chinese air force said in a not-very-reassuring statement.

“Rather than a fighter jet or two, numerous military aircraft with multiple functions passed over the Miyako Strait before they carried out this mission. This is by no means something that happens regularly,” military expert Zeng Zhiping of the Nanchang Institute of Technology told the SCMP.

The Japan Times reports that Japan’s Self-Defense Force scrambled its own fighters during the exercise after four of China’s bombers, two of its fighters, and two recon planes flew over the Miyako Strait.

China’s Global Times noted that “news of the drills comes a day after the USS Mustin came within 12 nautical miles of Meiji Reef in the Nansha Islands in the South China Sea,” not-so-subtly implying that the exercises were made larger and/or more aggressive in response to the latest American freedom of navigation patrol.