General Stockwell appeared during season 5. In The Court Martial series of episodes The A-Team were captured by the US Army and faced a court martial followed by death. It was Stockwell who aided their escape from the firing squad, although he may have initiated the capture in the first place. He then made The A-Team work for him in a fixed number of operations before they would receive a full pardon.
Stockwell was a rather shady character to say the least. It was unclear which of America's governmental branches he worked for.