Well, most "World Wars" start out as a series of separate wars that correlate as the major combatant nations join the fight. Japan was fighting in Manchuria and China in the 30's. Italy in Ethiopia. Germany was "assisting" Franco in Spain. The starting date for WW2 is generally accepted as 9/1/1939, but you could make an argument that it was already going on for several years.
“Most world wars”:
In fact, what you said is much what I meant. All are different but much the same in that they began as small incidents or grievances with each building on one another. We have flash points in the Middle East, Southern Asia, Africa along with the economic situations, religious conflicts and cultural clashes and civil war rumblings which ebb and flow. Wars and rumors of war.