It's said that big doors swing on little hinges. This may be a good example. On April 6th at Shiloh, Confederate General A. S. Johnston planned to hit the left flank of Grant's unsuspecting army and drive it away from the Tennessee River into the swamps to the north. 1/11

It was a good plan, as by coincidence Grant's left was his most vulnerable spot, guarded only by a single small brigade. Prior to the battle, Johnston wrote president Davis that his army would line up for battle with his largest corps, under Braxton Bragg, on the far right. 2/11

This again was a good plan, as it dovetailed perfectly with his goal of loading up on the right and slamming into Grant's dangerously under-strength left before help could arrive. His remaining three corps would support the main attack.... 3/11

Pinning down the rest of the Union army and preventing them from reinforcing the main point of attack. So the attack formation was to be, from left to right, Polk's corps, Hardee's corps, Bragg's corps, with Breckinridge and his small corps in reserve. 4/11

But that's not what happened. Take a look at this map from the American Battlefield Trust. In the lower-left you can see the Confederate attack formation prior to the battle as it looked when the battle actually began. Compare it to the formation that Johnston outlined. 5/11

So what happened? Why was the original formation scrapped in favor of the new one? Did Beauregard simply change the orders on his own, or did Johnston approve the new plan? Strangely, and to the best of my knowledge, no one really seems to know, from that day to this. 6/11

The man in the best position to know – P.G.T. Beauregard, Johnston's second-in-command who took over after Johnston was killed – never said. It was and still remains quite possibly the greatest mystery of this battle. And maybe its biggest mistake. 7/11

Shiloh was a nightmare for everyone involved, and a great many things went wrong on both sides. Yet perhaps nothing on the Confederate side looms quite so large as this change in formation before the battle ever began. 8/11

Johnston's plan was not without perils of its own. Especially the terrain involved, which was (and still is) the roughest on the battlefield. In the actual event though, his men managed to slog their way through that very ground after a hard fight during the afternoon. 9/11

They likely could have done so that morning as well. Would this have won them the battle? There's no way to know that. But given how things actually went and how close a call it was, anything tipping the balance more in their favor could only help. 10/11

We may never know why the formation was altered, and I'm not saying it cost them the battle before it began. There are always unknowns. But they did themselves no favors when they inadvertently tipped those delicate scales a bit toward the Union side before the first shot. /End.