[Pelham]

Lincoln issued a Proclamation three days after Ft Sumter that is as close to a Declaration of War as you will find concerning the Civil War:

https://www.visitthecapitol.gov/exhibitions/artifact/proclamation-president-united-states-april-15-1861

In it he also calls for Congress to convene a special session on July 4, 1861, where he gives his reasoning for calling up and using the army:

http://teachingamericanhistory.org/library/document/message-to-congress-in-special-session/

What you don’t find in either of these is a mention of fighting to end slavery. Lincoln is waging war against rebellious fellow Americans in order to preserve the Union. He is fighting to put down secession.

[DiogenesLamp]

This is exactly correct. In the past I have asked these people who are justifying the North invading the South, to show me military orders that mention abolishing slavery in the initial stages of the war.

There aren't any.

They made that lie up later. When they started the war, it was to stop the South trading directly with Europe and bypassing their rigged system to funnel money into New York and Washington DC.