More than 40 ships and submarines representing 15 international partner nations travel in formation in the Pacific Ocean during the Rim of the Pacific (RIMPAC) 2014 exercise in this U.S. Navy photo taken July 25, 2014, and released July 31, 2014. REUTERS/U.S. Navy/Mass Communication Specialist 1st Class Shannon E. Renfroe/Handout

More than 40 ships and submarines representing 15 international partner nations travel in formation in the Pacific Ocean during the Rim of the Pacific (RIMPAC) 2014 exercise in this U.S. Navy photo taken July 25, 2014, and released July 31, 2014. REUTERS/U.S. Navy/Mass Communication Specialist 1st Class Shannon E. Renfroe/Handout

More than 40 ships and submarines representing 15 nations in formation during the RIMPAC 2014 exercise in this US Navy photo taken July 25, 2014. REUTERS/U.S. Navy/Mass Communication Specialist 1st Class Shannon E. Renfroe/Handout

February 25, 2016 9:15 AM (UTC+8)