Japan is marking the 60th anniversary of the bombing of Nagasaki. At least 70,000 people died in the world’s second nuclear bombing, when a plutonium device was dropped on the city.In a ceremony in the city, water was poured over the memorial stone in memory of the dead, many of whom died crying out for something to quench their thirst. There is fresh debate over why the bomb was dropped just three days after a bomb using uranium as its core was dropped on Hiroshima, killing 140,000 people. Some critics say the Americans wanted to test their plutonium device, while others say it was necessary because Japan had not surrendered. The bomb had the same force as 21,000 tonnes of conventional explosives, its intense heat killing victims instantly. The twin nuclear attacks are seen as having foreshortened the end of World War II in the Pacific. By August 14, 1945 the Japanese had agreed to sign an unconditional surrender on board the USS Missouri, anchored in Tokyo Bay.