He got back to Mosby's Confederacy in time to learn of Lee's defeat at Gettysburg. Realizing that Lee's retreat would be followed by a pursuing Union army, he began making preparations to withstand the coming deluge. For one thing, he decided to do something he had not done before--concentrate his force in a single camp on the top of Bull Run Mountain. In the days while Lee's army was trudging southward, Mosby gathered every horse and mule and cow he could find and drove them into the mountains, putting boys and slaves to work herding them. He commandeered wagons, and hauled grain and hay to his temporary camp. His men erected huts, and built corrals for horses and a stockade for prisoners. They even moved a blacksmith shop to the hidden camp. Then Mosby sat down and waited. A few days later, Meade's army began coming through. The Forty-Third Partisan Ranger Battalion went to work immediately. For two weeks, they galloped in and out among the Union columns, returning to their hidden camp only long enough to change horses and leave the prisoners they had taken. They cut into wagon trains, scattering cavalry escorts, burning wagons, destroying supplies, blowing up ammunition, disabling cannon, running off mules. They ambushed marching infantry, flitting away before their victims had recovered from the initial surprise. Sometimes, fleeing from the scene of one attack, they would burst through a column on another road, leaving confusion behind to delay the pursuit. Finally, the invaders passed on, the camp on the mountain top was abandoned, the Mosby men went back to their old billets, and the Forty-Third Battalion could take it easy again. That is to say, they only made a raid every couple of days and seldom fought a pitched battle more than once a week. The summer passed; the Virginia hills turned from green to red and from red to brown. Mosby was severely wounded in the side and thigh during a fight at Gooding's Tavern on August 23, when two of his men were killed, but the raiders brought off eighty-five horses and twelve prisoners and left six enemy dead behind. The old days of bloodless sneak raids on isolated picket posts were past, now that they had enough men for two companies and Mosby rarely took the field with fewer than a hundred riders behind him. Back in the saddle again after recovering from his wounds, Mosby devoted more attention to attacking the Orange and Alexandria and the Manassas Gap railroads and to harassing attacks for the rest of the winter.