On September 10, "with a smart little army of about fifteen hundred", Lane started northward along the Missouri line. His avowed objective, however, was not to pursue Price but to "clear out" the valley of the Osage and to "pitch into" the towns of Butler, Harri­sonville, Osceola, and Clinton. On September 12 he reached Trading Post, Kansas, and from there turned eastward into Missouri. As soon as they crossed the border his men began to loot, burn, and perhaps murder and rape.

The climax of Lane's march occurred at Osceola on Septem­ber 23. After exchanging a few shots with some Confederates on the outskirts, his men entered the town and proceeded to ransack it. They robbed the bank, pillaged stores and private houses, and looted the courthouse. Captain Thomas Moonlight bombarded this last building with a cannon, and others set fire to the town, almost totally destroying it. Many of the Kansans got so drunk that when it came time to leave they were unable to march and had to ride in wagons and carriages. They carried off with them a tremendous load of plunder, including as Lane's personal share a piano and a quantity of silk dresses. The "Sack of Osceola" henceforth was a prime cause of bitter hatred of Lane and Kansans by the people of West Missouri. 

[Lane's men are charged with committing murders and molesting women in the following sources: Charles Robinson, The Kansas Conflict (Lawrence, Kansas, 1898); John McCorkle, Three Years with Quantrill (Armstrong, Missouri, 1915); William H. Gregg, “The Gregg Manuscript”, (State Historical Society, Columbia, Missouri); John C. Shea, compiler, Reminiscences of Quantrell's Raid upon the City of Lawrence, Kas. (Kansas City, Missouri, 1879); Council Grove Press, September 14, 1863.]

[Lawrence Kansas State Journal, November 28, 1861; White Cloud Kansas Chief, October 6, 1864. One of Quantrill's men who participated in the Lawrence Raid of August 21, 1863, wrote years later that the raiders found three pianos in the parlor of Lane's home in Lawrence, two of which were recognized as having belonged to Southern people in Missouri. See McCorkle, Three Years with Quantrill.]