The way it looks to me, the general concept for Johnston's counterattack at Shiloh was pretty sound; he'd take on one Union army, right wheel to cut it off from support, destroy it against the Owl Creek swamps, before turning back to block the other army. He even had the good fortune to catch them completely by surprise.
Unfortunately for him, the deployment got all mucked up, with men from different corps getting mixed up, without enough men on the right wing to cut Grant off from Pittsburg Landing, and he was shot by his own men. Halleck took over the army and proceeded inexorably to Corinth, which served as a base for Grant's operations against Vicksburg.
So what happens if Grant's army is walloped at Shiloh, and Buell is prevented from crossing at Pittsburg landing? Can Grant's army be cornered, or will it just withdraw to the north? Johnston will probably lose a lot of his men even if he wins; what's his next move? Can a sharp defeat make a permanent career casualty of Grant?
Unfortunately for him, the deployment got all mucked up, with men from different corps getting mixed up, without enough men on the right wing to cut Grant off from Pittsburg Landing, and he was shot by his own men. Halleck took over the army and proceeded inexorably to Corinth, which served as a base for Grant's operations against Vicksburg.
So what happens if Grant's army is walloped at Shiloh, and Buell is prevented from crossing at Pittsburg landing? Can Grant's army be cornered, or will it just withdraw to the north? Johnston will probably lose a lot of his men even if he wins; what's his next move? Can a sharp defeat make a permanent career casualty of Grant?