The US and Japan initiated their biennial Keen Sword military exercise on Monday, marking one of the largest joint drills between the two countries. This year, the exercise will concentrate on Japan’s southwestern islands, including its westernmost island, Yonaguni, which is just 68 miles east of Taiwan.

Both the US and Japan have deployed new anti-ship missile systems to Yonaguni for the drills, escalating tensions with China.

US Marines have been stationed with the Navy-Marine Expeditionary Ship Interdiction System (NMESIS) on Yonaguni, granting them a range of about 115 miles, putting vessels patrolling the coast of eastern Taiwan within reach.

According to The Associated Press, Japan has deployed its first long-range Type-25 land-to-ship missile to the island, with a range of about 620 miles, enabling it to target mainland China from Yonaguni.

The US has also positioned a HIMARS rocket system on Ishigaki, approximately 150 miles from Taiwan, where the opening ceremony for Keen Sword occurred.

HIMARS can strike targets up to 190 miles away if equipped with ATACMS missiles, though the type of ammunition the system was deployed with remains undisclosed.

US Forces Japan stated in a release that the exercise will involve 45,000 Japanese troops, 11,000 US troops, as well as forces from Australia, Canada, France, Germany, the Netherlands, New Zealand, and the Philippines, with observers from South Korea and the UK.

Song Zhongping, a Chinese military expert, warned in an article for China’s Global Times that the US deployment of a new missile system on Yonaguni heightens the risk of miscalculation between the US and China, potentially prompting Beijing to conduct its own military drills in the area.

The South China Morning Post previously reported that China has bolstered coast guard and naval activities east of Taiwan in response to maritime boundary discussions announced in May between Japan and the Philippines.