The conflict was a bitter one, marked by atrocities such as the executions and torture of American prisoners of war by the Imperial Japanese Army and the desecration of dead Japanese bodies. Both sides interred enemy aliens. Superior American military production supported a campaign of island-hopping in the Pacific and heavy bombardment of cities in Okinawa and the Japanese mainland. The strategy was broadly successful as the Allies gradually occupied territories and moved toward the home islands, intending massive invasions beginning in fall 1945. Japanese resistance remained fierce. The Pacific War lasted until September 1, 1945, when Japan surrendered in response to the American atomic bombings of Hiroshima and Nagasaki – among the most controversial acts in military history – and the Soviet entry into the Asian theater of war following the surrender of Germany.