[cowboyway]

It was about putting down an insurrection

What insurrection? When did the Confederacy try to destroy the US government?

and preserving the Union.

When it's done at gunpoint it's called 'subjugation'. (look the word up if you're not entirely sure of the definition)

However, secession was 100% about slavery

That's the affirmative action, politically correct, revisionist yankee version, alright.

without secession there would have been no war.

Correction: without Lincoln's invasion there would have been no war.

[rockrr]

Now that’s revisionism pokie. You know better.

[Ditto]

sub·ju·gate  –verb (used with object),-gat·ed, -gat·ing.
1.to bring under complete control or subjection; conquer; master.
2.to make submissive or subservient; enslave.

in·sur·rec·tion  –noun
an act or instance of rising in revolt, rebellion, or resistance against civil authority or an established government.