Drills in east and southeast Asia are designed to demonstrate readiness against any future Chinese aggression.
ADVERTISEMENTUS, Thai, and South Korean marine forces stormed ashore on a Thai beach on Friday as part of the three countries' annual Cobra Gold military exercise.
The scenario was an operation to seize and hold a beachhead against an opposing force.
With support from low-flying jets and a naval barrage, marines from the three countries came ashore on Hat Yao beach in Chon Buri province, about 180km south of Bangkok.
Thai marines led the way, followed by the South Koreans and the Americans.
“The most important thing for these exercises is building the relationships so that we do that here in training and if we face a real world event together we know the people and we’re ready to respond," said US Rear Admiral Christopher Stone, commander of the Expeditionary Strike Force.
"I’m looking for the proficiency of our teams but the relationships are enduring.”
Cobra Gold was first held in 1982, and has grown into one of the world’s largest multinational military exercises.
Though only three countries took part in the marine landing on Friday, many others are involved in other aspects of the training, which ends on 8 March. These include Japan, Singapore, Malaysia and Indonesia.