The Union capture of Vicksburg (and Port Hudson) in July, 1863, gave the North control over the whole Mississippi River, isolating the Confederate states west of this river: Arkansas, Louisiana, and Texas. In addition, the Union controlled most of Mississippi and Tennessee by this time. This accounts for five out of the original eleven Confederate states.
Did this effectively reduce the "Confederacy" to the six states east and north of Mississippi? Or did the five western states somehow manage to send troops and supplies to the six eastern ones and thereby remain active in the war? Or did say, the three states west of the Mississippi River at least form a defense perimeter and fight on "locally," independently of the others?
Put another way, had a situation been created where defeating the six eastern states automatically meant winning the war?