Who was the last American executed for desertion under fire?

Edward Donald "Eddie" Slovik was arrested several times as a minor. Already at the age of 12 he was arrested for the first time for breaking into a foundry. Eddie's minor crimes came one after another: petty thefts, disturbing the peace. breaking and entering. He was sent to prison twice, in 1937 (he was paroled in 1938) and in 1939. Eddie's criminal record made him unfit for duty in the military, and in 1942 Eddie got married and started living with his wife's parents. He didn't expect anything more than that, but destiny had other plans for him. A year after the wedding, Slovik was reclassified as fit for duty and subsequently drafted by the Army.

That's how Eddie became the only American soldier to be court-martialled and executed for desertion since the American Civil War. Although over 21,000 American soldiers were given varying sentences for desertion during World War II, including 49 death sentences, Slovik's death sentence was the only one that was actually carried out. The death penalty was rarely imposed back at the time, and those cases typically were for rapes or murders. Slovik was the only soldier executed who had been convicted of a "purely military" offense.