Complex sentence: He is best known for his command of Camp Sumter, the Confederate prisoner-of-war camp near Andersonville, Georgia; he was tried and executed after the war for conspiracy and murder relating to his command of the camp.
Split into simpler sentences: He is best known for his command of Camp Sumter, the Confederate prisoner-of-war camp near Andersonville, Georgia. After the war, he was tried and executed for conspiracy and murder relating to his command of the camp.