Further change emerged.

Since 1941 US had been secretly developing new weapon to end war atomic bomb.

  • part of state funded nuclear development programme called Manhattan project.
  • US decided to keep it from USSR until Potsdam conference in July 1945.
    • At conference Truman privately informed Stalin that US had successfully tested atomic bomb

Stalin not surprised when Truman told him about bomb. Info about Manhattan project leaked to USSR earlier. US choice to not tell USSR about bomb further deepened Stalin’s suspicion towards US’s intentions.