War in Iraq was started because we need oil and refused to leave until we got it all.
World war 1 started due to economy at the time, growth of nationalism, balance of power, old territorial disputes, the Balkan wars, and many more reasons. Plus Britain and Germany had a huge rivalry.
World war 2 started because Germany invaded Poland and other countries intervened to stop Germany from spreading even more, thus causing a battle.
The cold war started because it was a capitalism/democracy type situation, and no one knew if they were gonna drop bombs on eachother.
The war in Afghanistan started because U.S Was basically pointing fingers at Afghanistan for causing 9/11.
The mexican/American war was caused over land because the mexicans were mad that the U.S was taking their land.
The Nez Perce and White war was caused because Whites were taking Indian land, and they refused to give it up.
These are just the wars I can think of at the top of my head, and they were some pretty big wars. None of them involved religious beliefs.
My source? School and Google.