On September 6, 1862, William Quantrill led a surprise raid of guerrilla Confederates against the city, which resulted in a half dozen deaths and the destruction of most of the city. Quantrill captured the outpost and tried forcing the men to swear an oath to the Confederacy. The oath was deemed invalid in November 1862, since the guerrillas were not considered legitimate enemy military units. Kansas militia continued to occupy the Olathe military post through the rest of the Civil War.