Union General Ulysses S. Grant won several victories around Vicksburg, Mississippi. The fortified city was considered essential to the Union's plans to regain control of the Mississippi River. On May 22, Grant began a siege of the city. After six weeks, Confederate General John Pemberton surrendered, giving up the city and 30,000 men.
Grant and his army crossed the Mississippi river and drove the confederate army of Lt. General John C. Pemberton into the defensive lines surrounding the city
After Vicksburg and Port Hudson fell, the spinal cord of the Confederacy was severed. This reopened the Mississippi River to the North, opening up that trade route.
After Vicksburg and Gettysburg, the diplomatic scales tipped in favor of the North.
Britain and France stopped all aid they were giving the South and by the end of 1863, all Confederacy hopes of foreign aid was lost.