Nuclear Weapons
The bombs dropped on Hiroshima and Nagasaki had been developed by American and British scientists working together, but soon after the Second World War, Britain found itself out of the loop with the US no longer willing to collaborate. The Soviet Union tested their own nuclear weapon in 1949. And the United States was on its way to testing the first H- bomb, 1000 times more powerful than the bomb dropped on Hiroshima.
Credit Imperial War Museums