Correct, skipy, religion (or sometimes official atheism's attack on religion) has always been used to drive war forward. That's not the fault of religion itself, however, nor is it the fault of atheism itself, it's the fault of extremely ambitious and ruthless men in government and media who are quick to use anything and everything they can to drive a war forward...for their own gain.

So what do they use? Whatever will work. They use...

Patriotism

Fear of other cultures

Genetic Racism

Cultural racism

The excuse that "they were going to attack us someday, so we'll attack them first"

False flag "attacks" (that didn't really happen or were not perpetrated by the other country that is being attacked)

ecomomic incentives -there's much money to be made in wartime

Political theories - such as Naziism, Communism, the "Free World", Fascism, Maoism, etc

Religion (you have already focused on that, so I hardly need to elaborate)

Past grievances - They did this horrible thing then. Therefore they deserve to be attacked by us now.

Rumors of theoretical threats (like Saddam's nonexistent WMDs)

Declarations of altruistic intent - the USA pretended it was going to war with Spain in 1898 to help Cubans! What a grand pretense. They didn't do it to help Cubans at all, they did it because Cuba and the Phillipines were very rich islands in Spanish possession, full of economic gains to be made if the USA could get them, plus it would give the rapidly expanding American fleet some very handy major bases in both the Caribbean and the Pacific, thus making the USA for the first time a global power...and Spain was a doddering, weak old military power which couldn't possibly win such a war. So the US government convinced its public that it was going to war for altruistic reasons, and to avenge the Maine (which may have indeed been sunk by someone, but I highly doubt it was the Spanish...they were desperate to avoid a war with the USA).

There was no religious reason behind that war was there? Nope. Just the usual reasons of economic, territorial, and strategic gain for the aggressor.

The sinking of the Maine may have been a "false flag" attack accomplished by American agents. It may have been done by Cuban revolutionaries to trigger American intervention on their side. It may have been an accident, due to spontaneous combustion in the coal stores (such things happened to warships on quite a number of occasions back then, and similar things even happened in WWII...the Japanese lost a major battleship to an internal explosion of unknown cause while it was sitting peacefully at anchor one day in 1943). At any rate...I doubt that the Spanish did it.

Religion didn't cause that war. But I bet almost every pulpit in America backed it vociferously. They didn't do so because religion started the war, though, they did so because they probably believed the US government propaganda and were in a frenzy of patriotic fervor.

It's governments who start wars, and they do it for their own gain.