WW2 was fought, for a large part on something closely resembling religious basis.*Cough* WWI *cough* WWII *cough*
To state that wars are fought 'in the name of' some deity or other is a little skewed.
Most are fought for purely territorial motives.
The war can actually be broken down into 4 different wars: The war in the Pacific, the western Allies versus the Germans, the Germans versus the Soviets and the Germans versus "the Jew".
Those last two were easily the most horrific and destructive and were fought on something resembling religious beliefs, there was just no god involved.