There was a division of thought at the start of the raid. Price, and perhaps Kirby Smith, looked upon it as an invasion intended to restore southern control of the state. I think Price's subordinates more realistically looked upon it as a combination raid/recruiting expedition/diversion of federal forces from the eastern campaigns.

Price didn't have enough men to seize Missouri and even if he had recruited enough men, there was no way he could arm, feed and equip them. The Confederacy, absent control of the MS River, simply couldn't support a large army in central Missouri like the feds could. The feds could always use their control of the waterways (and thus St. Louis) to send in the force that would eject the Confeds from the MO River theater of operations in the center of MO--just like they did after lexington.