In January 1863, Stuart, with Lee's concurrence, authorized Mosby to form and take command of the 43rd Battalion Virginia Cavalry. This was later expanded into Mosby's Command, a regimental-sized unit of partisan rangers operating in Northern Virginia. The 43rd Battalion operated officially as a unit of the Army of Northern Virginia, subject to the commands of Lee and Stuart, but its men (1,900 of whom served from January 1863 through April 1865) lived outside of the norms of regular army cavalrymen. The Confederate government certified special rules to govern the conduct of partisan rangers. These included sharing in the disposition of spoils of war. They had no camp duties and lived scattered among the civilian population. Mosby required proof from any volunteer that he had not deserted from the regular service, and only about 10% of his men had served previously in the Confederate Army.