<P> The massive research and development demands of the war included the Manhattan Project, the effort to quickly develop an atomic bomb, or nuclear fission warhead . It was perhaps the most profound military development of the war, and had a great impact on the scientific community, among other things creating a network of national laboratories in the United States . </P> <P> In 1942, and with the threat of invasion by Germany still apparent, the United Kingdom dispatched around 20 British scientists and technical staff to America, along with their work, which had been carried out under the codename Tube Alloys, to prevent the potential for vital information falling into enemy hands . The scientists formed the British contribution to the Manhattan Project, where their work on uranium enrichment was instrumental in jump - starting the project . </P> <P> The invention of the atomic bomb meant that a single aircraft could carry a weapon so powerful it could burn down entire cities, making conventional warfare against a nation with an arsenal of them suicidal . Following the conclusion of the European Theater in May 1945, two atomic bombs were then employed against the Empire of Japan in August during the Pacific Theater, effectively terminating the war, which averted the need for invading mainland Japan . </P> <P> The strategic importance of the bomb, and its even more powerful fusion - based successors, did not become fully apparent until the United States lost its monopoly on the weapon in the post-war era . The Soviet Union developed and tested their first fire weapon in 1949, based partially on information obtained from Soviet espionage in the United States . Competition between the two superpowers played a large part in the development of the Cold War . The strategic implications of such a massively destructive weapon still reverberate in the 21st century . </P>

Advancements in technology led to what new theater of battle