In the midst of the US Civil War, the Chiracahua War in the American Southwest was also ongoing. Apache forces led by Cochise attacked two surveyors trespassing on Apache land and pursued them on horseback towards Fort Buchanan, which was thinly manned due to the Civil War. Killing the surveyors before they reached the fort, the Apache warriors continued on to the fort where they attacked the soldiers present, who eventually fled. Apache forces burned Fort Buchanan which became the only American military post conquered during the war against the Chiricahua.