Emphasis added above. Now the claim is being made that Lincoln, at some point, decided to use the war to end slavery because of moral and perhaps religious beliefs, not just military necessity as others have claimed. If true - and there is evidence to support the claim - Lincoln was using the military to violently overthrow the pro-slavery U.S. constitution (with an eye toward tidying things up with a constitutional amendment after the war.)
The first thing pro-war advocates should learn is to never, never admit Lincoln used the military to violently overthrow the pro-slavery U.S. constitution.
Lincoln also used the Military to violently overthrow the even more pro slavery Constitution of the Confederate States of America.
He used the US military to suppress a insurrection, which the constitution explicitly gives him the power to do. Much the same way that George Washington used the military to suppress the Whiskey rebellion.
Congress used the constitutional process of amendments to end slavery in the country.
From Day One, the US Constitution protected slavery where it was lawful in Union states.
That could only be changed by constitutional amendment.
By contrast, states & regions in rebellion had no such protections and could have their "property" declared "contraband of war" for military reasons.
At least that was the theory reportedly given to young Lincoln during his brief time in Congress (1848) by old Founder John Quincy Adams.
And it's what Lincoln did after the Confederate declaration of war on the United States, May 6, 1861.
Pretty much sums it up.