The United States Army hasn't executed a soldier since April 13, 1961.
John A. Bennett was hanged for the rape and attempted murder of an 11 year old Austrian girl.
In the entire 20th century only 135 Service Members total were executed. Mostly for purely criminal offenses during WWII.
The only Soldier who was executed for a strictly military offense since the Civil War was Slovik. He was executed for desertion on Jan 31 1945
The author of The Execution of Private Slovik, William Bradford Huie interviewed one member of the firing party for the book and let that one account be representative of all of them to protect the firing party's privacy.
When Eddie Slovik was executed his firing squad was drawn by lot from the unit he deserted. It wasn't voluntary and one of the firing partu claimed he was told that if he refused the assignment He would be shot.
The interviewee also stated that the M1 he used was dirty and kicked hard. he said that there wasn't any question in his mind that he had live ammunition. He also said the guy that drew the blank knew he had a blank because the blank didn't cycle the bolt in his M1.
There were 12 men on Slovik's firing party. He was at 11 times all in the upper chest and shoulders and died within two minutes.
We don't execute people anymore.