July Crisis

After the murder of Archduke Franz Ferdinand, Vienna resolved to settle accounts with Serbia. On 5 July Wilhelm II promised Austria-Hungary his full support, and on 23 July Serbia received an ultimatum with a 48-hour deadline. Although Belgrade's reply was largely conciliatory, Austria-Hungary broke off relations and declared war on Serbia on 28 July.

From then on the crisis ran on two clocks, diplomatic and military. British proposals for a conference came to nothing, Russia ordered general mobilisation, Germany declared war on Russia and France, and the invasion of Belgium on 4 August brought Britain into the war. Within five weeks a local Balkan conflict had become a European war.