Moscow and Beijing conducted large-scale naval drills in the Sea of Japan this week, Russia’s Pacific Fleet announced in a statement to journalists on Sunday. The three-day exercise involved a wide range of activities, including joint firing drills, a simulated naval battle, and air defense training.

The ‘North/Cooperation-2023’ exercise was held over July 20-23, the fleet’s press service said. It involved two Russian anti-submarine war frigates and two Chinese destroyers, as well as a pair of both Russian corvettes and Chinese guard ships alongside a number of support vessels, the statement said.

A total of 30 aircraft from both nations also took part in the drills, the fleet said, adding that this included anti-submarine planes and helicopters, interceptors and other maritime aircraft, the fleet said. The two nations’ naval groups took part in some 20 combat exercises during the drills, it added.

The drills were aimed at “strengthening the naval cooperation between the Russian Federation and the People’s Republic of China as well as maintaining peace and stability in the Asia-Pacific Region,” the statement said.

A U.S. Navy briefing slide is calling new attention to the worrisome disparity between Chinese and U.S. capacity to build new naval vessels and total naval force sizes. The data compiled by the Office of Naval Intelligence says that a growing gap in fleet sizes is being helped by China’s shipbuilders being more than 200 times more capable of producing surface warships and submarines. This underscores longstanding concerns about the U.S. Navy’s ability to challenge Chinese fleets, as well as sustain its forces afloat, in any future high-end conflict.

The most eye-catching component of the slide is a depiction of the relative Chinese and U.S. shipbuilding capacity expressed in terms of gross tonnage. The graphic shows that China’s shipyards have a capacity of around 23,250,000 million tons versus less than 100,000 tons in the United States. That is at least an astonishing 232 times greater than the United States.