The Battle of Gettysburg is generally considered the turning point of the war. General Robert E. Lee has invaded the North in hopes of bringing pressure on the North which would then hopefully agree to a negotiated peace; in fact the Confederate Vice Preisident, Alexander Stephens was dispatched at the same time ostensibly to discuss prisoner exchanges but speculation is he also was to discuss terms of peace. President Lincoln refused Stephen's request to cross enemy lines and no meeting took place. Gettysburg was the bloodiest battle of the war; and at its conclusion, the initiative lay completely with the North, even though the war continued another two years.
The Battle of Vicksburg is important because it marked the culmination of an important part of the Anaconda Plan, namely to cut the South in two by capturing the Mississippi River. It was a difficult battle and General Ulysses S. Grant was forced to lay seige to the town until it finally surrendered. With the fall of Vicksburg, the Union controlled the entire Mississippi River, and the third of the Confederacy on the west side of the river was completely cut off.