<P> The Siege of Vicksburg (May 18--July 4, 1863) was the final major military action in the Vicksburg Campaign of the American Civil War . In a series of maneuvers, Union Maj. Gen. Ulysses S. Grant and his Army of the Tennessee crossed the Mississippi River and drove the Confederate Army of Mississippi, led by Lt. Gen. John C. Pemberton, into the defensive lines surrounding the fortress city of Vicksburg, Mississippi . </P> <P> Vicksburg was the last major Confederate stronghold on the Mississippi River; therefore, capturing it completed the second part of the Northern strategy, the Anaconda Plan . When two major assaults (May 19 and 22, 1863) against the Confederate fortifications were repulsed with heavy casualties, Grant decided to besiege the city beginning on May 25 . After holding out for more than forty days, with no reinforcement and supplies nearly gone, the garrison finally surrendered on July 4 . </P> <P> The successful ending of the Vicksburg Campaign significantly degraded the ability of the Confederacy to maintain its war effort, as described in the Aftermath section of the campaign article . Some historians--e.g., Ballard, p. 308--suggest that the decisive battle in the campaign was actually the Battle of Champion Hill, which, once won by Grant, made victory in the subsequent siege a foregone conclusion . This action (combined with the surrender of Port Hudson to Maj. Gen. Nathaniel P. Banks on July 9) yielded command of the Mississippi River to the Union forces, who would hold it for the rest of the conflict . </P> <P> The Confederate surrender on July 4, 1863, is sometimes considered, when combined with Gen. Robert E. Lee's defeat at Gettysburg by Maj. Gen. George Meade and retreat beginning the same day, the turning point of the war . It cut off the states of Arkansas, Louisiana, and Texas from the rest of the Confederate States, effectively splitting the Confederacy in two for the duration of the war . The Union victory also permanently severed communication between the balance of the Confederacy and the Trans - Mississippi Department . </P>

What was the result of the battle of vicksburg