Annual joint drills aimed at strengthening security in the Indo-Pacific region got underway in Indonesia on Thursday.
Nearly 5,000 troops are taking part. They come from 15 countries, including Japan, the highest number on record.
Indonesia and the US held the first "Garuda Shield" joint drills in 2007. They've been called "Super Garuda Shield" since last year, when the number of participating countries was increased.
On Thursday, the troops gathered for the opening ceremony at an Indonesian marines training center in eastern Java.
Japan's Ground Self-Defense Force is sending around 280 personnel. It plans to conduct drills with five nations, including Australia, Singapore and Britain. They will practice retaking captured islands.
Ueda Kazumasa, Chief of Staff for the Japanese Ground Component Command, said the environment surrounding Japan is extremely severe and it's important to deepen cooperation with countries sharing the same values and security interests.
Yudo Margono, Commander of Indonesian National Defense Forces, says the host nation doesn't limit the number of countries and offers them the chance to take part.
Southeast Asia is at the center of the strategically-important Indo-Pacific region.
The Indonesian government wants to strengthen its multilateral security ties, as China expands its maritime activities in the region.