Charlie Company, 1st Battalion, 20th Infantry, were the first to arrive in My Lai on March 16th 1968. Its men came to Vietnam in December of 1967, most of them volunteering for the draft. Nearly half of the men were black, eighteen to twenty years of age and only a few had gone to college for even a year. Out of the 130 men in Charlie Company thirteen of them had not done well enough on the Army's basic intelligence tests to qualify for service but were excepted by a new program called Project 100,000. Project 100,000 provided remedial education to those who were not eligible for the Army, but none of the men in Charlie Company were exposed to any education before being shipped off to Vietnam.
The company's commanding officer was Captain Ernest Medina. Captain Medina was enthusiastic about killing Vietcong, he was happy to be in Vietnam to help win a war he believed in. Charlie Company respected and admired there captains especially, Lieutenant William Calley. Lieutenant Calley was eager to please Captain Medina but Medina never really thought much of anything Lieutenant Calley did. Lieutenant Calley was said to have a bit of an attitude problem. One of Calley's favorite lines was "I'm the Boss". .
At 7:22 A.M., March 16, 1968, Charlie Company entered My Lai by helicopter. My Lai is a tiny village on the northeastern coast of Vietnam near the South China Sea. My Lai lies in the Vietnamese district of Son My, a heavily mined area of Vietcong entrenchment. Numerous members of Charlie Company had been maimed or killed in the area during battle in the preceding weeks. The agitated troops under the command of Lieutenant Calley entered the village ready for engagement with the elusive Vietcong. .
The troops of Charlie Company were told to kill everything. They had the ammunition to do so, armed with twice the normal load of rifle and machine gun ammunition. This type of mission was known as a "search and destroy" mission.