The highest number of fatalities in a single year during the Vietnam war for the United States army was 1968 when they lost 16,899 according to governmental archives. 1968 was the peak of casualties and they started gradually reducing the number of casualties until leaving the war. Out of 58 220, 16 899 died in 1968.
The Gulf of Tonkin incident happened in 1964 and was one of the main reasons why the United States army decided to intervene in the conflict in a more direct manner. Because of this incident, a declaration was made that the US president would use anything that he can in order to stop communism from spreading into the countries that were spreading communism.