On May 21, 1856, a posse of 800 Southerners surrounded the free soil capital of Lawrence, Kansas. They flew a blood-red flag on which was inscribed "Southern Rights." Over the course of the day they sacked the town, while the inhabitants fled. News of the guerilla war flaring in Kansas became the talk of the nation. Northerners began sending clothing and food to the embattled free-soil settlers.

In Washington, anti-slavery Senator Charles Sumner decried the spread of slavery to Kansas and accused Southerners of "raping and plundering the virgin territory." South Carolina Congressman Preston Brooks took offense. On the floor of the United States Senate, Brooks beat Sumner with the gold head of his heavy cane as Sumner struggled to free himself from his desk. Finally, blinded by his own blood, Sumner collapsed into the aisle, and lost consciousness. Brooks continued beating him until his cane broke.

Sumner would never fully recover. Newspapers across the South celebrated the assault, but when news of the incident reached John Brown's encampment in Kansas, he and his followers were enraged. When someone urged caution, Brown replied, "Caution, caution ... It is nothing but the word of cowardice." On the night of May 24th, 1856, Brown and four of his sons dragged five pro-slavery men from their cabins, and hacked them to pieces with broadswords.