August 30, 1860 – The Second Battle of Fort Defiance was a military engagement fought during the United States period of the Navajo Wars. On August 30, 1860, about 1,000 Navajo warriors assaulted the United States Army garrison of Fort Defiance in New Mexico Territory, now within present day Arizona. The Navajo achieved a surprise attack but was ultimately repulsed by 150 American defenders of the 1st Infantry under Captain Oliver Shepherd. The Americans formed in the center of the buildings and withstood the Navajo attack. The natives retreated with a loss of around twenty dead and several wounded while the Americans suffered one man killed in action and three wounded. The second Navajo assault on Fort Defiance was one of the largest battles fought within the borders of Arizona. It was also one of the reasons why the militia commander Lieutenant Colonel Manuel Antonio Chaves ordered an unauthorized campaign into Navajo territory in 1860 and 1861.