The U.S. and Japan are playing war games near the U.S. island of Guam, as their alliance deepens.

The destroyers Mustin and McCampbell are exercising with about half a dozen Japanese Maritime Self-Defense Force ships and training to hunt submarines and engage incoming fighters, in anti-ship, anti-aircraft and anti-conducting anti-surface, anti-air and anti-subsurface operations, according to a Wednesday press release.

The exercises will also include a maritime patrol aircraft, several EA-18G Growlers, designed for electronic warfare attacks, and a submarines. The release did not specify if the sub was American. which nation’s submarine it was, but the attack submarine Texas is deployed to the region and is currently on a port visit to Sasebo, Japan.

Guam Exercise, or GUAMEX, is an annual exercise with the JMSDF. Japan has been is taking a more assertive role in regional security in the wake of provocations from China, which has built islands out of reefs in the South China Sea and imposed an air defense identification zone over the East China Sea.

Japan, The country, led by its Prime Minister Shinzo Abe, has been is revisiting its constitution and weighing changes that would allow Japan to take part in combat operations with coalition partners like the U.S.

Japanese naval officials have also said they might begin patrolling the highly contended contentious South China Sea alongside U.S. warships. China continues to with the United States as China continues to assert claims to international waters that neighbors and the U.S. view as excessive, creating flashpoints as China builds a modern navy. seen by the United States and its neighbors as excessive.

Since the end of World War II, Japan’s constitution has barred their its armed forces from combat beyond self-defense, a reaction to Imperial Japan's brutal conquest of its neighbors. has prohibited it’s using their armed forces except when acting in self-defense.

Japan has one of the world's largest navies, with more than 120 ships to include destroyers, amphibs and attack submarines. Japan's latest moves signal that those ships could sail with U.S. ships and task forces, like the forward-deployed carrier strike group based in Japan.