Total casualties from all sides and fronts—including war's civilian losses—approximately 41 million. 23 million injured, 18 million killed. Between 9 and 11 million soldiers have died in battle; other accounts put the number at 12 million. Of those, around half are missing and assumed dead. Artillery fire instantly obliterated a large number of troops. Some nations are difficult to obtain accurate statistics from. During World War II, some nations preserved weak archives, some destroyed their records, and some just disappeared. However, we do have the rough estimates above.
The answer is McCarthyism.
During this period, the U.S. was determine to prevent the spread of
communism in its territories.
Surveillance and warrantless arrest of suspects were rampant. Many lost their careers after being branded a
communist while others were put in jail.
Many criticized this actions as unconstitutional.