After the war, he participated in the Nuremberg trials. One of Brigadier Foster's most admirable actions involved the liberation of the Nazi death camps. Initially, well-meaning Allied forces simply liberated the camps and moved on to their next objective. As a result, many of the weak and starving prisoners simply died. When Foster learned of this problem, he had several direct meetings with Winston Churchill with the result that an effective procedure was put in place to provide the prisoners with needed care and protection.