Given the task definition and input, reply with output. In this task, you are given a context paragraph, a question based on that and corresponding answer of a question. Your task is to generate supporting fact/knowledge from context paragraph which helps in answering a given question.

William Bedford Royall (April 15, 1825 December 13, 1895) was a Union Army officer during the American Civil War and later a United States Army brigadier general. Born in Virginia, he led a group of mounted volunteers from Missouri during the Mexican War. He became a first lieutenant of the United States Cavalry on March 3, 1855 and a captain on March 21, 1861. Despite his southern birth and his uncle Sterling Price's decision to join the Confederacy, Royall remained loyal to the Union and served in the Army of the Potomac. After the civil war, he served in Kansas under General George Crook. He retired on October 19, 1887 and died in Washington, D.C.. Question: What was the Apache nickname given to General under which William B Royall served? Answer: Nantan Lupan
After the civil war, he served in Kansas under General George Crook.