Right After WWII

Well, right before the war ended, the U.S. created and developed the technology for the atomic bomb. The U.S. told all of their allies, except one. Guess who that was? The Soviet Union! We didn't trust them, so we didn't tell them about it. Simple as that. Then Stalin found out and got really mad. We also didn't tell him about the Hiroshima or Nagasaki bombings. That also made him mad. We didn't tell them about it because we didn't want them to know about the atomic bomb. They would want that technology and we didn't want to give it to them. It would give them a chance to use it against us in the future. Then he trusted us as much as... Well, he really didn't trust us at all. The relations between the U.S. and the Soviet Union got just that much worse.