After weeks of near-starvation for besieged Union troops in Chattanooga, Grant ordered General George Thomas to seize Orchard Knob, a low hill in front of Confederate lines. The surprisingly easy Union success set the stage for the dramatic assaults on Lookout Mountain and Missionary Ridge that followed, shattering Confederate General Braxton Bragg's army and opening the path for Sherman's Atlanta campaign.
By late November 1863, Union troops trapped in Chattanooga had been reduced to quarter rations, their supply lines choked by Confederate forces holding the high ground on Lookout Mountain and Missionary Ridge. Grant, newly placed in overall command in the West, had already engineered the opening of the 'Cracker Line' to bring in food, but he needed to break the siege entirely.
On November 23, he ordered General George Thomas's Army of the Cumberland to test Confederate strength at Orchard Knob, a modest rise in the middle of the valley. What began as a reconnaissance turned into a full assault; Union troops advanced in parade-ground formation, stunning Confederate defenders, and seized the position within about an hour with minimal losses.
The capture of Orchard Knob gave Grant a forward command post and crucial momentum. Two days later, Union troops would famously scale Missionary Ridge in a seemingly spontaneous, unauthorized charge that routed Bragg's army, a battle historians still marvel at for its improbable success.