The rulers of Serbia were as “compliant” as humanly possible (more than they should have been) to Austria’s “Ultimatum” of July 23, 1914, and it still wasn’t “good enough”. Nothing that Serbia did or did not do would have prevented Austria from attacking her, because Austria was hell bent on crushing Serbia.
Well, she should have rethought that desire, because in the end, it was the Austro-Hungarian Empire that was “crushed” and dissolved.
Wilhelm II is a bit of a complicated case. While on the one hand he was pushing for war, on the other, when war was actually becoming a very real possibility, he started backtracking. By that time though, the wrecking ball was not to be stopped.
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Actually as I recall it Serbia was compliant as you say, and things would have passed with Austria, but then Russia stepped in and guaranteed the safety of Serbia, so the Serbs backtracked which pissed off the Austrians.
At that point the dice were cast because of the interlocking system of mobilizations. Austria mobilized, so Russia mobilized (could have been vice versa), then Germany, then France, and there goes the powder keg.