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What if Johnson wasn't wounded at Seven Pines, and Lee didn't get the opportunity to take command?

What if instead McClellan is too ill to command at all, or failing that we manage to get McClellan wounded or killed, and replaced by a more aggressive subordinate on the spot? Perhaps Sumner would work?

It seems to me like the position of the Union army at this time is such that you wouldn't need a great commander to take Richmond at this juncture, just one who wasn't afraid to use his men aggressively or at least not passively. Without McClellan's nerves, there's a confident and organized Union army at the gates of Richmond, and the Confederates, if little else changes, will probably mess up the initial engagements as OTL in their attempts to repulse the Union.

If Richmond does fall here, then where would that leave the Confederacy?
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