Castle Bravo
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of "Operation Castle". Detonated on March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon. Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving Li, which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll.
Castle Romeo
It was detonated on March 27, 1954, after several delays (which played havoc with the planned experimental measurements program) at Bikini Atoll of the Marshall Islands, on a barge moored in the middle of the crater from the Castle Bravo test. It was the first such barge-based test, a necessity that had come about because the powerful thermonuclear devices completely obliterated the small islands following detonation.