Operation "Prime Starfish" blew up a 1.4 megaton thermonuclear bomb 250 above Johnson Atoll in 1962. The radiation even damaged low orbit
communication satellites, and a large electromagnetic pulse blew out street lights and telephones in Hawaii. The USA did a lot of pretty crazy, high
altitude tests over the Pacific.
"Operation Crossroads" in 1946, at Bikini Atol in the Marshall Islands was just the start of 66 bombs detonated there. A great article in the LA
Times described the series of tests and the sad after effects for the local native people.
"The United States arrived in force in February, 1944, when Marines waded ashore to begin beating the Japanese back across the Pacific. Three years
later, the United States took formal charge of the Trust Territory of the Pacific Islands under U.N. auspices. Military control was so strict that
non-Marshallese civilians were barred until the mid-1960s.
The reason was nuclear weapons. From 1946 until 1958, the United States detonated 66 atomic bombs at Bikini and Eniwetok atolls, the most massive
atmospheric testing program in history.
Hundreds of islanders suffered severe burns, hair loss and vomiting. On Rongelap, which was covered by snowy clouds of radioactive coral dust after
the 15-megaton "Bravo" hydrogen bomb blast on Bikini in 1954, doctors found that 96% of children under 10 suffered thyroid abnormalities. Most
But a recent government review of 23 medical studies indicates that devastating long-term effects are still showing up.
A 1986 study showed that 91% of 314 Marshallese tested had radiation-induced blood disorders. More than half those tested in another study had
chromosome damage. Other researchers reported vastly increased rates of genital and thyroid cancer, leukemia and cataracts. One report found double
the normal rates of stillborns and miscarriages, including strange, spineless fetuses."
The US Navy discovered that ships don't hold up to atomic bombs, and thousands of sailors were exposed to damaging radiation. Only in the 80's were
the "nuclear veterans" deemed eligible for compensation by the US Congress.
The documentary film "Radio Bikini" gives a very interesting look at "Operation Crossroads" and its aftermath.