George, in March of 1861, Lincoln had not even assumed office yet, but many states had already seceded, based only on his election.

So if you ask me to speculate, to give my opinion, if there'd have been a war even had all slaves been emancipated, I'd say yes. Unless those departing states returned by their own choice, under some type of negotiation, at that point war was all but inevitable.

The war was for Union, or Separation, depending on the point of view. The secession, however was over slavery.