Regiments Split Into Different Theaters?

[Josh The Lighthouse Guy]

I just read that the 3rd Indiana Cavalry was split into two battalions - one in the Army of the Potomac and one in the Army of the Cumberland. Why was this done?

It wasn't simply a delayed transfer; the regiment was split in 1862 and never reunited.

I know the batteries within artillery regiments were frequently scattered. But what other infantry or cavalry regiments were split like the 3rd Indiana between different armies/theaters?

Note: I'm not looking for splits within a theater/army. Obviously, a regiment's companies might be scattered at different outposts for garrison duty or a few companies detached on escort duty.

 

[Dan Kohli]

This existed in a similar form for the US 11th through 19th Regular Infantry during the Civil War. Each regiment was to have three eight-company battalions; what essentially was a "depot battalion" at the regimental headquarters; and -- later in the rwar -- an "invalid battalion." The 11th US Infantry, for instance, had two field battalions in the field, a third field battalion organizing at regimental headquarters (essentially the depot battalion), and an invalid battalion at HQ as well.

It is my impression is that the third battalion of the 9 "New Army" infantry regiments were the battalions meant to be the depot battalions. Only 5 of the 9 regiments were able to recruit enough men to raise the three battalions.

 

[Stryker65]

So we're there technically (2) 3rd Maryland Regiments in 1864 and 1865 but just serving in different Corps which would be in different Armies ?

Technically, yes...but the detachment in Georgia was tiny, and was led by just two lieutenants IIRC. Colonel Joseph M. Sudsburg and Lieutenant Colonel Gilbert P. Robinson led the majority of the unit in Virginia.

 

[Stryker65]

Another example I thought of was the 14th Wisconsin Infantry: After veteran furlough expired, eight companies were immediately sent to Louisiana for the Red River campaign. Two other companies had not been fully formed at that time, and were ordered to come on as soon as they could; however, when they tried to go south as well, they were diverted at Memphis IIRC and sent to Sherman's army instead, serving with it through Atlanta, Savannah, and the Carolinas.