In the summer of 1863, Maj. Gen. Ulysses S. Grant’s Army of the Tennessee converged on Vicksburg on the Mississippi River, investing the city and trapping a Confederate army under Lt. Gen. John Pemberton. The city was located on a high bluff, and Union occupation of the town was critical to control of the strategic river. Grant's bold 6-week campaign began in early June and took his army south through Arkansas opposite Vicksburg, crossed the river 30 miles below the city, captured the Mississippi capital of Jackson, turned west and pushed Pemberton's army into Vicksburg itself. By mid-May, Pemberton's men had constructed a series of trenches, forts, redans, and artillery lunettes in a 7-mile ring surrounding the city. Grant's army surrounded Pemberton and outnumbered him two to one. Wasting no time, Grant launched two major assaults on May 19th and 22nd and was repulsed with heavy casualties. On May 25th, Grant decided to besiege the city. With no reinforcements coming, food and supplies nearly gone, and after holding out for more than forty days, Pemberton finally surrendered on July 4th. Grant's Vicksburg campaign was one of the most brilliant of the war. With the loss of Pemberton’s army at Vicksburg and the Union victory at Port Hudson five days later, the Union controlled the entire Mississippi River and the Confederacy was effectively split in half. Grant's victory boosted his reputation, leading ultimately to his appointment as General-in-Chief of the Union armies.