In fact, the Confederacy laid claim and attempted to "take over" Union states and territories of Maryland, Kentucky, Missouri, Oklahoma, New Mexico and Arizona, as well as Union sympathizing areas of secessionist dominated states in Western Virginia, Eastern Tennessee, Western North Carolina and parts of Arkansas.
Further, RE Lee's 1863 campaign into Pennsylvania was intended to not only decisively defeat the Union army, but also to establish a permanent base across the rail line junctions in the state capital of Harrisburg.
Such a base could threaten all major northern and western cities as well as provide supplies for the Confederacy.
If successful, why would they ever give that up?
So the Confederacy was as aggressive towards the Union as it could be -- often failed, but not for lack of trying.
Again, don’t color MD as simply a Federal state. It was heavily pro-south and basically divided. Lincoln knew he couldn’t be surrounded so sent in troops to hold it at gunpoint and later made sure pro-south politicians were arrested and unable to vote. Rather than run away and establish temp quarters as in earlier conflicts.
It’s disingenuous to glibly call it Fed territory, and I have little doubt similar situations existed in other of what used to be called border states.
You still can’t admit that invading territory for war purposes does not mean it is for permanency. Else we might have Canada, Mexico, Cuba, France, Germany, Japan, and Iraq. Why would we give any up?
I don’t think that they wanted Massachusetts LOL (but they did want New York City).
What a bunch of war-mongers.