In 1854, the
U.S. Congress had passed the
Kansas-Nebraska Act which stipulated that the residents of these territories would decide whether they wished to enter the Union as a slave or free state. This doctrine became known as
popular sovereignty. Organized groups from the
North sent thousands of abolitionist supporters to Kansas in an attempt to tip the balance in favor of free state advocates, to counter settlement from pro-slavery supporters from
Missouri. As a result, pro- and antislavery groups had frequent clashes culminating in the Battle of Black Jack. On May 21, 1856,
Henry Clay Pate participated with a posse of 750 pro-slavery forces in the
sacking of Lawrence. The next day, Congressman
Preston Brooks from South Carolina
physically attacked Senator
Charles Sumner of Massachusetts in the Senate chambers. Three days later, a band of men, led by John Brown and comrade Captain Shore, executed five pro-slavery men with broadswords at Pottawatomie Creek. This incident became known as the
Pottawatomie massacre. In response to the massacre, Pate, recently granted the title of "Deputy United States Marshal", set out with a pro-slavery militia to either capture or kill John Brown. They took prisoner two of Brown's sons (John Brown Jr. and Jason), as well as some other Free-State men. ==Battle==