Years before the Civil War began a number of battles were fought between Free-State advocates and pro-slavery men during the days of Bleeding Kansas, which often  included guerilla fighters. These battles included the Wakarusa War in December, 1855. An in 1856, a number of skirmishes occurred including the Sacking of Lawrence, Pottawatomie Massacre, Battle of Black Jack, Battle of Franklin, Battle of Fort Saunders, Battle of Fort Titus, Battle of Osawatomie, and the Battle of Hickory Point. The final major atrocity committed by Missouri bushwhackers before the outbreak of the war was the Marais des Cygnes Massacre in May, 1858.

During the early years of the Civil War the border line between the Northern and the Confederate states was infested by guerrillas. In a few instances these irregular soldiers favored the Union cause, but in a large majority of cases they were secessionists, and sometimes they cared more for plunder than they did for principle. William Quantrill was the most well-known of the  guerrilla leader in western Missouri and Kansas. Other men included Upton Hays, John Thrailkill, Coon Thornton, William "Bloody Bill" Anderson, Frank James, Cole Younger, Bill Todd, John Jarrette, George Shepherd, Dick Yeager, and numerous others. Several of these men were only privates, but by their daring and blood-thirsty deeds they won notoriety that has carried their names into history.

Upton Hays was in command of the "Partisan Rangers" in western Missouri until he was succeeded by William Quantrill in 1862. A number of raids were made by guerrilla gangs into Kansas over the years. In October, 1861, the town of Humboldt was raided by "Colonels" William Sherley Williams and John Matthews, who sacked nearly every house and store in the settlement. About the same time the little town of Gardner, in  Johnson County, was also plundered. On March 7, 1862, Quantrill raided Aubrey, a small town in the southeast corner of Johnson County, where he killed three men and destroyed considerable property. In June, Bill Anderson made a foray as far west as Council Grove, killing two men and burning at least one house. On September 6th and 7th, Quantrill visited Olathe, where he destroyed and carried off a lot of property, and in October he made a descent upon Shawnee in Johnson county, where seven citizens were killed. Just before visiting the town he attacked the camp of a Santa Fe wagon train and killed 15 members of the escort. Humboldt was again visited in 1862 -- this time by "Colonel" Talbot, who burned several buildings, plundered the town, and killed 4 or 5 citizens who tried to defend their homes.

The next event was the worst atrocity committed by the Missouri guerillas. On August 21, 1863, William Quantrill led some 300  men in the Lawrence Massacre, which  targeted Lawrence due to the town's long support of abolition and its reputation as a center for Redlegs and Jayhawkers. By the time Quantrill's men rode out of town, more than a quarter of the buildings had been burned to the ground,  the banks and stores looted, some 185-200 men were dead.

Just after the raid on Lawrence, Quantrill passed through the old town of Brooklyn, where he did some damage, and on October 6, 1863, his men ruthlessly massacred some Federal troops in the  Baxter Springs Massacre. Other depredations by guerrillas were in the vicinity of Mine Creek, where a number of settlers were driven from their homes, and at the towns of Potosi and Spring Hill.

The Lawrence Massacre as illustrated in

Harper's Weekly, September, 1863.