By the time the Army of the Ohio joined General William T. Sherman's Atlanta Campaign in 1864, it had already repelled Confederate attacks on Ohio and marched South through Tennessee, chasing John Bell Hood through the Battles of Knoxville and Nashville. After burning Atlanta, the Union XXIII Corps, which made up the bulk of the Army of the Ohio, stopped to create a historical wonder: the world's best battle trophy.
It turns out that Civil War combat isn't very kind to the remnants of battle flags, especially those of the losing side. And after years of constant fighting, and a whole lot of winning, the XXIII Corps had a lot of captured Confederate flags.
I don't know if you see where this is going.
With all the wear and tear on their own battle flag, the Army of the Ohio decided they required a new flag to fly as they might soon be helping General Sherman March to the Sea. You don't want to burn Savannah without looking your best. It's a good thing Confederate battle flags decided to use the exact same colors the XXIII Corps required for its flag.
Using the best pieces of the captured enemy flags they had, the Corps decided to form a new battle flag of their own, made entirely from the shredded, battle-scarred remains of their defeated enemies' banners. They even happened upon more of the cloth after capturing Macon, Ga. The finished product was actually made for them by the 98th Illinois Regiment.