Stalin was terrified at the news of the new weapon. He couldn't proceed with his plans to acquired lands in the pacific. So the war far over but the cold war begun as well as the weapons race.
first answer:
because he realized that mass distruction weapon would make the world socialist revolution impossible,cause the barricades,riots,labour strikes...allof that would be useless under the atomic fire.
second correct answer:
1. Stalin was worried that his future enemies (US & Britain) possessed superior weapons to the Soviets.
2. Stalin was concerned that the Japanese would surrender too soon. Stalin wanted to take as much Chinese, Korean & Japanese territory before the war ended.
3. Stalin wanted a Soviet occupation zone in Japan like he had in Germany & Austria.
He was concerned. The Soviet Union had an agenda but with those blasts, their plan was ruined.
The official reason for dropping the bombs were that the casualties in taking the Japanese mainland would be unacceptable. I believe that bomb was a show of strength from Truman to Stalin. Which Stalin pointedly ignored
President Truman.
1945
See atomic bombings of Hiroshima and Nagasaki
The mayor event was the dropping of the atomic bomb over Hiroshima.
It ended the war.
Hiroshima then Nagasaki .
See: Atomic bombings of Hiroshima and Nagasaki
The atomic bomb was dropped on Hiroshima and Nagasaki in World War 2.
See website: Atomic bombings of Hiroshima and Nagasaki
Stalin was angry
The dropping of two atomic bombs on Hiroshima and Nagasaki.