During the winter and spring, both sides occupied themselves with their favorite—and generally profitless—practice of sending cavalry on raids. Almost a third of Bragg's army consisted of cavalry—16,000 effectives versus about 9,000 Union. In a February raid against Fort Donelson (the Battle of Dover) Confederate Maj. Gen. Joseph Wheeler, commanding two brigades of cavalry, failed to capture the garrison in Dover, Tennessee or disrupt Union shipping on the Cumberland River. In March, Rosecrans sent a detachment to cut Bragg's communications, but it was forced to surrender in the Battle of Thompson's Station. Also in March, Confederate Brig. Gen. Nathan Bedford Forrest raided Rosecrans's communications at Brentwood, a station on the Nashville & Decatur Railroad, in the Battle of Brentwood. Confederate Brig. Gen. John Hunt Morgan made his famous raid into Indiana and Ohio, an operation that cavalry historian Stephen Z. Starr called "militarily insane", that ended in Morgan's capture. Confederate Maj. Gen. Earl Van Dorn who was brought into the Army of Tennessee's area of operation by Johnston, was unsure of his mission, in which he was supposed to take position, and of who would serve under him. He was unsuccessful in cutting Rosecrans's communications between February and May, with raids that included two minor cavalry fights north of Spring Hill in March, and Forrest's pursuit and capture of Col. Abel Streight in Streight's Raid in Alabama in April. In May, Van Dorn was murdered and Forrest assumed command of the cavalry on Bragg's left flank; most of Van Dorn's Mississippi troopers were transferred back to their home state in May. The Confederates lost 4,000 cavalrymen during this period but did cause Rosecrans some concern over his supply lines. The Union lost 3,300 men and received little in return.