Question

julius and ethel rosenberg were charged convicted and ececuted for

Answer 1

Espionage. They sent secrets during the Second World War from the Manhattan Project to Stalin, so that the latter coudl develop an atomic bomb. It is fortunate for their place in history that Stalin died in 1953, before he had a chance to use these weapons in a new war in Europe, as files later made available (after the fall of the Soviet Union) very strongly suggest he intended.

If the Rosenbergs had been partly responsible for enabling a nuclear World War III on the European continent in the 1950s, the blood of tens of millions would have been on their hands. As it was, Stalin died abruptly, and the resulting turmoil and caution in the new Soviet leadership turned the potential for a nuclear war into the Cold War.

However, there is very little doubt the surprisingly success of the Soviets in producing an atomic bomb as early as 1949 -- the direct result of atomic espionage, including that of the Rosenbergs -- prodded the United State (which had previously rejected the goal) into developing the thermonuclear bomb (the H-bomb).