Grant planned for a double envelopment of Bragg's forces at the Chattanooga campaign. Introduce PODs to completely surround the Confederate army. How would the double envelopment change history?
POD would be that Grant is given command over Banks as well and detach 10k more troops from the Gulf to him. Brings 10000 more troops to Chattanooga. He now has 70k. At look out mountain, these extra 10k swing around Sherman as Sherman engages Cleburne. They link up with Hooker to complete the encirclement of Bragg.
Bragg surrenders
With 70k troops
Grant details Sherman off with 20k troops to go after Longstreet in Eastern Tennessee. Longstreet is able to evade Sherman and makes it back to Virginia. Grant with 50k captures Atlanta in Jan 1864. He then detaches 10k from Atlanta to Mobile under Thomas with another 10k coming from New Orleans under Banks. Mobile is taken in April 1864. After Mobile, Banks conducts his Red River campaign. Thomas is occupation commander. Thomas details Sheridan to follow and destroy Forrest.
After Atlanta, Grant moves to the coast with 40k in two wings.
He captures Savannah and Augusta in March 1864.
After Savannah, Grant is now made commander of all field armies.
Grant captures Columbia, SC and Charleston in May of 1864
North Carolina falls in July of 1864
Meade and Lee face each other off in Virginia. When Longstreet meets Lee, Lee has him go on another Shenandoah raid to distract the Union. Grant orders Sherman to follow Longstreet back down the Sheandoah. Longstreet is able to hold a line halfway down. Sherman cannot advance further, but the route to the North is blocked from any further raids.
Grant and Meade encircle Richmond in July and August
Lee surrenders in September 1864
War is over in October