In January 2259, Sinclair was reassigned as ambassador to Minbar, where he took command of the Rangers. He was succeeded at Babylon 5 by Captain John Sheridan. In 2260, Sinclair received a 900-year old letter from himself on Minbar, revealing that he was not the "reincarnation" of Valen, as the Grey Council believed, but in fact Valen himself. Armed with this knowledge, Sinclair took Babylon 4 back with him 1,000 years to aid the Minbari in their first war against the Shadows, and in so doing, fulfilled Minbari prophecy by becoming the One Who Was. It was here that Sinclair used the triluminary to transform himself into a Minbari, thus fulfilling the legend about Valen being "a Minbari not born of Minbari", also explaining why the triluminary responded so strongly to him during his interrogation by the Grey Council, as it had been programmed to respond to his DNA.