From Halopedia, the Halo wiki
Vice Admiral Williams was a high-ranking officer in the UNSC Navy at the close of the Human-Covenant War, during which time he commanded the Third Fleet. On October 10, 2552, Battle Group Rhino, a battle group in the Third Fleet, detected twelve unidentified large vessels in the Sol system broadcasting outdated civilian IFF codes. Upon approach, eleven of the vessels made unauthorized slipspace transits from the Sol system. Pursuant to standing orders to engage vessels not positively identified as friendly, Battle Group Rhino moved to engage the remaining ship. The UNSC Totem Lake was subsequently lost with all hands after reportedly suffering multiple hull breaches and boarding parties. The battle group, under the direction of Captain W. Murray, then disengaged and regrouped at Phase Line Alpha above Enceladus. Vice Admiral Williams, requested permission from Fleet Admiral Harper to attack the ship, but permission was denied.