I agree with Non-Sequitur's point.
Many Northerners opposed the US Federal Government's invasion of an independent nation, the Confederate States of America. They even staged draft riots and so forth in order to protest the Federal Government's determination to conscript them into killing their fellow Americans.
A more fair and reasonable term would be that favored by my old Political Science professor, "The War of Federal Aggression".
The "North", after all, was by no means wholly united behind the Federal Government's determination to invade the Confederate States of America.
Many Southerners opposed the rebel governments illegal secession, too. But the 'independent nation' existed only in the minds of those supporting the Southern rebellion.
A more fair and reasonable term would be that favored by my old Political Science professor, "The War of Federal Aggression".
The most accurate term would be the one used originally, "War of Southern Rebellion".
That’s fair enough. Of course Lincoln did manage to put a large number of those Northerners in prison.