Germany actually surrendered twice during WW2 . On May 7,1945 and on May 9th. This was because of warning ideologies tussles between the soviet union and there allies. They also surrendered because they have already lost and they made everyone mad at them.
The Us tried to from an alliance with Germany but ended up making an alliance with the soviet union. They formed an alliance with the soviet union because the were both enemies with Germany.
The Manhattan project was a research and development in World war II. They produced the first nuclear weapons. It was lead by the United states with support of the UK and Canada. The Manhattan project produced the first atomic bomb.
On August 6th, 1945 , during world war II they dropped there first bomb over a Japanese city, Hiroshima. The bomb was a B-29 bomber. It immediately killed around 80,000 people. 10,000 people died later from radiation exposure.
On August 9th, a second bomb was dropped. B-29 on A city called Nagasaki. Estimated killing of 40,000 people. A few days after, Japan's emperor Hirohito announced over a radio that they are surrendering.
Japan surrendered because they were shocked at the end of WWII because of the bombs that the US dropped over them. They also surrendered because they didn't want to confess that they lost so they just Surrendered. September 2nd, 1945, V-J day was the day Japan surrendered in the WWII.