During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan, the first on August 6, 1945 and the second on August 9, 1945. These two events are the only active deployments of nuclear weapons in war to date.
For six months, the United States had made use of intense strategic fire-bombing of 67 Japanese cities. Together with the United Kingdom and the Republic of China, the United States called for a surrender of Japan in the Potsdam Declaration on July 26, 1945. The Japanese government ignored this ultimatum. By executive order of President Harry S. Truman, the U.S. dropped the nuclear weapon "Little Boy" on the city of Hiroshima on Monday, August 6, 1945, followed by the detonation of "Fat Man" over Nagasaki on August 9.
Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki link
The attack on Pearl Harbor (called Hawaii Operation or Operation AI by the Japanese Imperial General Headquarters (Operation Z' in planning) and the Battle of Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941 (December 8 in Japan). The attack was intended as a preventive action in order to keep the U.S. Pacific Fleet from interfering with military actions the Empire of Japan was planning in Southeast Asia against overseas territories of the United Kingdom, the Netherlands, and the United States.
The base was attacked by 353 Japanese fighters, bombers and torpedo planes in two waves, launched from six aircraft carriers. Four U.S. Navy battleships were sunk (two of which were raised and returned to service later in the war) and the four others present were damaged. The Japanese also sank or damaged three cruisers, three destroyers, an anti-aircraft training ship,and one minelayer. 188 U.S. aircraft were destroyed; 2,402 men were killed and 1,282 wounded.
The power station, shipyard, maintenance, and fuel and torpedo storage facilities, as well as the submarine piers and headquarters building (also home of the intelligence section) were not attacked. Japanese losses were light: 29 aircraft and five midget submarines lost, and 65 servicemen killed or wounded. link
Shockingly people seem to think the quake and tsunami is karma for the attack on pearl harbour.