The ultimatum was delivered at 6pm by the Austro-Hungarian ambassador to Belgrade, with a deadline of 48 hours within which the Serbian government had to respond. They accepted all but one of the numerous demands, which led Austria-Hungary to declare war three days later on 28th July. Austria-Hungary had been concerned about the growing power of Serbia, and was keen to find a way to weaken the government and stop it taking over the Southern Slavic populations of the northern Balkans, and especially Bosnia, under the banner of pan-Slavism. To the government officials who favoured war, the assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, on the 28th June was the perfect excuse. Following the assassination, Germany had given Austria-Hungary assurances that it would support military action against Serbia, in what is known as the ‘Blank Cheque’ of 5th July. Acting with the knowledge that the strongest army in Europe was on their side, the Austro-Hungarian Crown Council began to discuss how best to justify a war against Serbia. They decided that an ultimatum containing unacceptable demands would be the best course of action, and finally agreed the wording on the 19th. After Serbia’s refusal of the sixth point in the ultimatum, Austria-Hungary declared war. Although it was intended to remain localised, the network of European alliances that had developed from the late 19th Century soon saw the conflict develop into the First World War.