The first ever such exercise, AUMX, started on Monday at the Sattahip Naval Base in Thailand and wrapped up in Singapore.

The crew of No.18, a Pohang-class corvette South Korea gifted to Vietnam last year, was part of the combined task group alongside the Philippine Navy’s BRP Ramon Alcaraz and the Royal Brunei Navy’s KDB Darulaman.

Under the command of the BRP Ramon Alcaraz with Captain Hilarion Cesista at the helm, No.18 ship participated coding and decoding of electronic versions, light communication, night cruises, and aerial photographic exercises.

It also performed a visit, board, search, and seizure (VBSS) drill and was on sentry duty for the other vessels.

The drills come at a time of increased U.S. engagement with the region and tensions between Beijing and Southeast Asian nations over the South China Sea.

The AUMX was proposed by former U.S. Defense Secretary Jim Mattis at a meeting with his 10 ASEAN counterparts on the sidelines of the ASEAN Defense Ministers Meeting-Plus in 2017 in the Philippines.

The proposal was approved at the ASEAN Defense Ministers Meeting a year later in Singapore, and it was agreed that AUMX will only take place once and not on a regular basis.

Eight warships, four aircraft and more than a thousand personnel from the U.S. and all 10 ASEAN countries took part in the exercise.

Last October the Vietnamese navy sent its frigate, 015 Tran Hung Dao, to participate in a five-day joint naval exercise with ASEAN and China at Zhanjiang City, Guangdong Province. The event was aimed at fostering stability and relieving tensions in the region.

In June last year Vietnam sent eight naval officers to Hawaii to participate in the 2018 Rim of the Pacific (RIMPAC) Exercise, the world’s largest multinational naval drill, held every two years.

Participating in the one-month maritime exercise were 47 surface vessels, five submarines, 18 national land forces, and more than 200 aircraft and 25,000 naval forces.