The mountain was won, in the end, by being abandoned. Through the night of November 24, Bragg (South) made the calculation that decided the whole campaign: he could not hold everything, and what he needed to hold was Missionary Ridge, the long eastern crest where his main army and the climactic fight would be. So he ordered the Lookout Mountain force withdrawn in the darkness, pulling the survivors and the reinforcements alike down off the mountain by the Summertown road, which had stayed open, and east across the valley to the ridge. The night handed the retreat a strange gift: a brilliant full moon, riding high over the mountain, slid into the blackness of a total lunar eclipse in the small hours, the very hours Bragg’s men were filing off the summit. Veterans on both sides would remember it for the rest of their lives. The Confederates, slipping away into a reddened dark, read it as an omen of doom; the Federals below read the same red moon as a sign of the enemy’s ruin. The summit that the country was already turning into a legend was given up under an eclipse, without a shot. By dawn, there was no Confederate army left on Lookout Mountain at all.

The most famous image of the battle is, on close inspection, the gentlest. At first light on November 25, a patrol from the 8th Kentucky Infantry (North) climbed to the point of Lookout Mountain, the mountain’s northern tip, the prow that overlooks the river, and found it empty. They walked up the last of the mountain unopposed, climbed to the highest rock, and raised the United States flag on the summit, where the whole army in the valley below could see it. A great cheer rolled up from the thousands who had spent the previous day staring at the cloud. It is one of the indelible pictures of the war: the Stars and Stripes on the point of Lookout Mountain at dawn, a flag raised on a height nobody had fought for, planted by men who had walked, not stormed, to the top. It looked like a conquest. It was a quiet morning walk up an emptied mountain to plant a flag for an audience. The image outran the action, exactly as the name had.

With Lookout Mountain cleared, the campaign turned to its real climax, and Hooker (North) turned with it. His orders for November 25 were to come down off the mountain, push across Lookout Valley, and strike the southern end of Bragg’s line on Missionary Ridge while the rest of Grant’s army hit it head-on. That was the decisive day, the day the siege of Chattanooga would truly be broken. Hooker, as it happened, was delayed crossing the valley and arrived late; the ridge was carried in a famous, half-ordered charge by the Army of the Cumberland, the same men beaten at Chickamauga, surging up the slope on their own momentum. Lookout Mountain cleared the western board and set the table. Missionary Ridge is its own battle.

What Lookout Mountain actually bought was less than its legend, but not nothing. Tactically it was a clean, low-cost Union win: Hooker’s force took the western height and over a thousand prisoners for under 700 losses of their own. Strategically it was one piece of lifting the siege, not the decisive blow; it cleared the western peak and the river-and-rail approaches and freed Hooker to swing against the ridge the next day. Some historians, noting that Hooker’s delay kept his men from playing much part at Missionary Ridge, go so far as to call it effectively a drawn battle whose real payoff was the cleared board and the morale jolt, a defensible reading. What is not in doubt is the larger meaning.

The larger meaning is the door. Lifting the siege of Chattanooga opened the rail gateway to the Deep South, and through that gateway, in 1864, would march William T. Sherman’s army on the road to Atlanta and, beyond it, the March to the Sea, the campaign that drove a blade through the heart of the slaveholding South and helped break the system the whole war was fought over. So this small fight on a foggy mountain, the one Grant called all poetry, was one of the hinges of that door. The flag the 8th Kentucky planted at dawn flew over an emptied summit. But the valley it overlooked was now the open road into the country the Confederacy had gone to war to keep enslaved. The poetry was overrated. The door it helped open was not.