One of the great "what ifs" I've often wondered about is "what if" Van Dorn had regrouped his army following Pea Ridge and actually made it across the Mississippi and joined Johnston at Corinth prior to Shiloh? 15,000 tough Trans-Mississippi troops added to the 44,000 he marched into Tennessee with might just have tipped the balance in his favor. It is included as as option in the old SPI TSS-based game: Shiloh: Bloody April, but honestly, I never played the option enough to convince me one way or another...