To address the title, on the same side of a war, or any thing that has people on “sides” different people have different reasons for being on the same side.
We Nat Turner abolitionists were changing from Quakers, Amish, Mennonites and other non-violent preferences to churches that condoned violence because we saw slavery as such an evil practice that it was the ultimate justified war.
The fire and brimstone churches pushed war.
Others were more refined. They rationalized “to save the union”.
But look at Iraq. In the 2000 election Bush explicitly rejected “nation building” which was being advocated by Cheney and the neo-cons. But post-911 Bush flip-flopped to give the neo-cons the green light. Their motivation was not WMD.
But WMDs was the Democrats boogeyman. So it was cynically used to get their support for the same war. Different motivations, same side in the war.
I’m late to this debate. You’re a Nat Turner abolitionist? Didn’t turn out well for old Nat as I remember...
Of my four great-grandfathers alive during the Civil War, one was fresh off the boat from Europe, didn't speak much English but enlisted in the 119th Illinois Infantry Regiment, served the entire war, marched nearly 2,000 miles, was captured & wounded but, thank God, survived.
Two of my great-grandfathers were Mennonite conscientious objectors, also farmers who stayed home and did what they knew best: farmed.
The fourth was older, had a young family and lawfully hired a replacement, whose fate we don't know...
My point is, we all come from many threads making a tapestry picture of who we are.
And wars are started for reasons we may or may not understand, but our duty as citizens under the Constitution is to serve when called according to our best abilities.