Germany and Britain were engaged in a bitter naval arms race, France had never forgiven Germany for inflicting a crushing defeat on it in 1870–71, and Russia was engaged in sabre-rattling with Austria-Hungary and Turkey over the fate of the Balkans and its southern borders.
What made matters worse was the fact that these powers had now aligned themselves into two heavily armed camps, with France, Britain and Russia on one side, and Germany, Austria-Hungary and Turkey on the other.
All it needed was a spark to set the powder keg alight. That duly arrived on 28 June 1914 when Gavrilo Princip, a Serbian nationalist, assassinated Archduke Franz Ferdinand, heir apparent to the Austro-Hungarian throne, in Sarajevo. Within a matter of days, Austria-Hungary, with Germany’s backing, had accused Serbia of sponsoring the killing and Russia and France had declared their support for Serbia.
Then, on 4 August, Britain was drawn in when German troops advanced west through Belgium. The war had well and truly begun.