PEARL HARBOR, Hawaii — Some 25,000 sailors and other military personnel from 22 nations are converging on Hawaii starting Friday to practice hunting for submarines and catching pirates in the world's largest naval exercises.

The U.S. Pacific Fleet is hosting the Rim of the Pacific exercises, which take place every two years in Hawaii and surrounding waters.

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Countries from Japan to Tonga and Russia to Chile are sending 42 surface ships, six submarines and 200 aircraft to participate in the series of drills, which takes place over the next five weeks.

Participants will train to clear mines, dispose of explosives and come to the aid of civilians in natural disasters, among other drills.

Adm. Cecil Haney, the Pacific Fleet commander, said the drills help different nations prepare for emergencies.

This year's exercises come as the U.S. refocuses its attention on the Asia-Pacific region.