Essentially a Mexican standoff where what was to be a small isolated conflict grew to involve the major powers of the day because of a web of agreements, alliances and treaties. It's really a fascinating story how Germany and Austria-Hungary wanted to squash the Yugoslavians but had to defeat France in order to go to war against the Russians who were in alliance with the Serbs but in order to do so had to use Belgium which was protected by Great Britain.
All to have their plan not work.