I wanted to know if there are any general terms for the outbreak of war, or ones which refer specifically to events near the beginning of the World Wars.
I think that they are generally referred to as war pretext incidents:
in July 1917, Duan used the incident as a pretext for declaring war on Germany.
The anti-war movement must address the issue of the “pretext” and “justification” to wage war.
Regarding the MH17 Malaysian airline crash, is the Obama administration in the process of “creating a war pretext incident” directed against Russia as part of propaganda campaign, which could lead the World into a World War III scenario?
Also false flag (or black flag) may refer to operations meant to start a war:
covert operations designed to deceive in such a way that the operations appear as though they are being carried out by entities, groups, or nations other than those who actually planned and executed them
In its most modern usage, the term may also refer to those events which governments are cognizant of and able to stop but choose to allow to happen (or "stand down"), as a strategy to entangle or prepare the nation for war.
Countries are also said to be on or to go on "a war footing", that is, they are prepared or are preparing, financially, industrially, and socio-psychologically, for the eventuality of war. The very preparedness for war can lead to war : the military industrial complex can make billions from it, and a bellicose people is an impulsive people.
The "shot heard round the world" is a phrase referring to several historical incidents, including the opening of the American Revolutionary War in 1775 and the assassination of Archduke Franz Ferdinand of Austria in 1914.
The latter refers to the beginning of World War One. WWII was just the the obvious sequel; to be continued.
Spark is a good word for the causation of conflict; sparked a war.
- anything that activates or stimulates; inspiration or catalyst. -Dictionary.com