The southern Japan island of Okinawa has marked the 68th anniversary of a decisive and bloody World War II battle that accelerated Japan’s surrender but left the island with a heavy U.S. military presence that is still the source of intense friction and frequent protests.

More than 200,000 people are believed to have died in the 1945 battle for Okinawa and it was the largest amphibious assault in the Pacific War of World War II. The 82-day-long battle lasted from early April until mid-June 1945.

Roughly 50,000 U.S. troops are stationed in Japan under a mutual security pact. About half, including thousands of U.S. Marines and a major Air Force base, are located on Okinawa. Protests against the U.S. troops are common on Okinawa amid concerns over crowding, troop-related crimes and the danger of accidents.