Both the Union and Confederacy knew control of the Mississippi River was critical to the war. Union forces mounted major military operations to take over Vicksburg, with General Ulysses S. Grant launching the Shiloh and Corinth campaigns and the siege of Vicksburg, from the spring of 1862 to the summer of 1863. The most important was the Vicksburg Campaign, fought for control of the last Confederate stronghold on the Mississippi River. The fall of the city to General Grant on July 4, 1863, gave the Union control of the Mississippi River, cut off the western states, and made the Confederate cause in the west hopeless.