What Nukes Have Done to the Marshall Islands

The impact of the Castle series. The most significant health and environmental impacts of US nuclear activities in the Marshalls were caused by six thermonuclear weapon tests conducted between March 1 and May 14, 1954 and known as the Castle series. Totaling some 48 megatons of explosive force, they had enormous negative impacts around the world. The first explosion, known as Bravo, produced an explosive yield of approximately 15 megatons—or 1,000 times the destructive power of the Hiroshima atomic bomb. Because of its size and other factors, Bravo also spawned what the US Radiochemical Society describes as “the worst radiological disaster in US history.”