On Sunday, the militaries of both China and Russia allegedly began carrying out joint air and sea drills in the Sea of Japan.

According to the Daily Caller, a Chinese naval fleet met with Russian Navy vessels and Kremlin aircraft to conduct the exercises, which were described in a statement by the Chinese defense ministry as a measure to ensure “safeguarding the security of strategic waterways.”

The operation, which is codenamed “North/Interaction-2023,” saw five Chinese warships and four ship-borne helicopters sent out to meet up with the Russian military. This marks the sixth time overall since 2019 that Russian and Chinese military forces have patrolled the Sea of Japan together. But it is the first time that both air- and sea-based branches of the Russian military have cooperated bilaterally with Chinese maritime defense forces.

Earlier this year, a joint drill by the two militaries was being carried out just 100 miles off the coast of Alaska, in the Bering Sea, when the United States Coast Guard happened upon the scene.

The governments of China and Russia first agreed to a strategic partnership in February of 2022, with the aim of “countering the influence of the United States.” The agreement was reached shortly before Russia invaded Ukraine. Allegedly, one of the earliest negotiations in this agreement was that Russia would hold off on its invasion of Ukraine until after the conclusion of the 2022 Winter Olympics in Beijing, so as to not take the international spotlight away from China’s achievements; the Olympics ended on February 20th, and the invasion of Ukraine began on February 24th.

“Friendship between the two States has no limits, there are no ‘forbidden’ areas of cooperation,” said the two countries in a joint press release at the time of the agreement.