Still in the midst of "July 1914" and one of the passages made me think. Could Austria have kept the invasion of Serbia to a localized conflict if the Dual Monarchy had mobilized and invaded Serbia right after the assassination of the Archduke?
It may seem preposterous, but the approach has merits. If the Austrians had invaded immediately after, than the act would be seen as direct result of the killing of Franz Ferdinand, instead of a power grab to reduce Serbia to a client state. There were plenty of voices urging just this, most notably Conrad and other Austrian cabinet members. So why did it take almost a month to send the ultimatum to Serbia, a month in which the goodwill and sympathy of Europe had dissipated? It was the work Of Tisza, the leader of the Hungarian government that slowed down the process. Since the unique structure of the Dual Monarchy meant that the approval of both Austrian and Hungarian governments needed to approve such decisive action, Tisza put the brakes on the whole process. To be fair, there were other factors, such as the fact that Austrian divisions had been dispersed to complete the yearly harvest, but these only came into play after Tisza began to drag his heels.
Though acting with the best of intentions, Tisza did eventually cave into the demands of the more belligerent members of the government, and a series of demands were dispatched to Serbia, demands that the Austrians hoped would be rejected and provide them an excuse for invasion. Thus, he cost his government nearly a month before they could take action against the Serbs. This delay ensured that the invasion and ultimatum were seen as Austria settling old scores with the Serbs, while cynically using the killing of Franz Ferdinand to mask their objectives. Of course this was the case, and would have been true even if the Austrians had invaded in the immediate aftermath of the murder.
In my opinion, the possibility of the Entente letting Austria mobilize against Serbia, even if undertaken in anger, would have been remote. This would have challenged the balance of power in the same way that the later Austrian mobilization did, and it is unlikely that the Powers would have let this happen.