They may not do parole but they will let you rejoin. When I was in the Navy I spent some time working with a man who, when he was in the Air Force, murdered his commanding officer and was sentenced to 20 years. He said that during his court martial there was plenty of testimony that the guy was an alcoholic and a bully but that wasn't an excuse to kill him. I don't know if he completed his full sentence but they did let him join another branch of service when he got out.
When I was in the Army, a guy reported for duty with our battalion who had been convicted of manslaughter in the Real World. The S-2 had paperwork processed for his discharge in less than a week. He went from basic to AIT to personnel center to a one week tour on “active duty” and out.
How in the Hell would you like to be commanding officer of a guy who killed his last CO? We also had a black guy who dropped out of PT formation and was sneaking back into the barracks. His platoon commander lit out after him and was tightening him up when another brother who had drawn rifle and ammunition for American Express guard detail (back in the day, our remote unit had a traveling American Express branch twice a week). The guard make a remark about what he would do if someone talked to him like that when he had a rifle. That really set the young LT off. After the guard refused to surrender his weapon, the LT physically relieved him of it and placed him under arrest. The young man was court-martialed as fast as paperwork could be processed.