Ships, submarines and aircraft from the United States and 38 allied nations will gather in the Pacific Ocean off Southern California and Hawaii this month for the world’s largest naval exercise, the Navy announced Tuesday. The biennial Rim of the Pacific Exercise — RIMPAC for short — involves 38 surface warships, four submarines, 170 aircraft and 25,000 military personnel. The exercise brings together naval and marine forces from the leading democracies in the region, including Japan, South Korea, Singapore, India, Australia and New Zealand as well as the United States, Canada and Mexico. RIMPAC 2022, scheduled to take place June…