Expansion of it was.
Nobody waged a war to defend something that did not need defending.
The Southern leaders of the time would disagree with you.
If anybody thought it did, the first thing Lincoln and the Northern dominated Congress offered was slavery effectively forever by express constitutional amendment.
Said offer being made after the Southern states had seceded and after they adopted a constitution that protected slavery to an extent never dreamed of by Thomas Corwin.
No it wasn't. It wasn't going to expand anywhere within the US. The evidence indicates "expansion" is a made up fake issue.
Said offer being made after the Southern states had seceded and after they adopted a constitution that protected slavery to an extent never dreamed of by Thomas Corwin.
Cause the USA was only a little pregnant. Not whole hog pregnant like the CSA.
Some in the Southern states argued slavery was threatened. Others pointed out they would be much better off financially if they were independent.
There is no escaping from the facts that the Northern states were quite willing to protect slavery effectively forever and the original 7 seceding states turned down their offer. Clearly something other than concerns over slavery must have been motivating them.