Chickamauga, September 19-20, 1863
POD: Colonel John Wilder was promoted to Brigadier General for his outstanding work during the Tullahoma Campaign.
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At about 1 PM on September 20, General Wilder rode north with his brigade of mounted infantry, armed with 7-shot Spencer repeating Carbines. He recently heard the sounds of ighting suddenly shift to the west - bad news for him as that probably meant the Union line had given way. He arrived just in time to hit some of Hindman's and Hood's people in the left flank, disorganizing them, and giving the broken remnants of Sheridan's and Davis' divisions time to retreat along with the whole XXth and XXIst corps supply trains.
Then up rode Assistant Secretary of War Charles Dana. He had just come from where the breakthrough occured and was quite lost. After inquiring of Wilder's command, he demanded that Wilder escort him and the supply trains back to Chattanooga, believing the battle to be lost.
iOTL: Colonel Wilder, unsure of the authority of this civilian, reluctantly agreed to an extent. He provided the escort, then remained behind and allowed another thousand-odd stragglers to not be captured, as well as the large Union hospital at Crawfish Springs. But he had really wanted to go on the attack, he and his men believing that the could break right through the Confederate lines.
iTTL: General Wilder tells off this frightened blubbering idiot in no uncertain terms. He provides a small escort for the man to get back to Chattanooga, then sets up his men as he planned to attack: 1 regiment each facing right and left moving forward obliquely, 3 stacked regiments facing forward. All of his men were on foot but had plenty of ammunition.
The Confederate advance, by this time, had stalled in the Dyer field, a victim of its own success. With most of the Union right wing in full retreat, it was taking time for the Confederates to reorient their lines to the north, in the direction of the rest of the Union army. There was no coordination - Hood having just been wounded again. General Kershaw, commanding Hood's division, was moving northward unsupported, and broke one line of Union artillery, but was then slowed and disorganized by a valiant stand by Harker's brigade. Meanwhile, Generals Brannan, Negley, and Wood were using the bought time to rally a scratch line on Snodgrass Hill and the ridge to the west.
Wilder's attack was a complete surprise and hit the newly forming Condeferate lines in the rear. He breaks through, near the junction of Kershaw's and Bushrod Johnson's divisions. In the process his men are flanked on both sides and so suffer heavy casualties. But they inflict as bad as they take, with no organized resistance to their front and the ability to fire seven times before reloading. They reach the Snodgrass homestead dimished in number but supremely high in morale, and with 2 Confederate brigades shattered behind them.
General Thomas, running over from the main line in the Kelly Field, sees these developments. With many heartfelt thanks to Wilder, he asks him to hold the extreme right of the Union line, along the wooded Horseshoe Ridge. The next unit in line is the 21st Ohio, which ironically is armed with Colt 5-shot revolving rifles, an experimental hybrid weapons.
Wilder's men, plus the 21st, easily face off Johnson's division for the first few assaults, while the rest of the line deals with Kershaw's and McLaws' uncoordinated attacks. Union General Granger arrives with a division of the reserve corps and is told to relieve some of Brannan's men facing Kershaw. This in turn frees them up to take over for Wilder, who in turn shifts even farther to the west to counter the later assaults of Preston's division.
What utimately decides the conflict is ammunition - the Confederates have more on hand, and after desperately fighting all afternoon, the Union's supply is exhausted. Thomas conducts the retreat, which is for the most part orderly, though a few units do get lost/left behind/captured. The Confederates are in little condition to pursue.
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The result: The Confederates take maybe up to 1000 more casualties than iOTL, the Union *possibly* up to 500 more (Wilder was just substituting for Granger on the ridge, so his division doesn't lose 25% casualties on the OTL flank counterattack - this partially offsets his losses for the northward attack).
What is significant is the decisive role played by the repeating rifles of all sorts. Thomas is effusive in his praise for the weapons, as are all the other Generals who serve on Horseshoe Ridge.
Also, if Wilder continues to show such good service in the Chattanooga Campaign (perhaps facing off Wheeler during the October raid), he may get promoted again, to Major General. If that happens he has a significant role in the cavalry for the 1864 campaigns.
So 2 major changes: 1st: Wilder vs. Forrest, with the Union cavalry armed with repeaters a year early. He certainly seems at least as good as anyone else in the Union cavalry arm in the west (we'll quibble about Sheridan elsewhere - but of course at the time, Sheridan was a division commander of infantry).
2nd: May be harder to pull off - but it would be cool to see a large-scale rearming of Union infantry with repeating rifles in time for the 1864 campaigns. If that happens the TL could go anywhere, including beyond the war.