Great Britain declares war on Germany

The European conflict becomes a world war

The Schlieffen Plan foresaw the invasion of France through Belgium to enable German forces to bypass a string of French forts and thus open the road to Paris. The implementation of this plan on 4 August 1914 was a clear violation of the Treaty of London of 1839, to which Prussia – and thereby Germany – was a signatory, and led Great Britain to issue an ultimatum demanding that Germany agree by midnight to respect Belgian neutrality.

Refusing to comply with the British demand, German forces moved into Belgium, committing atrocities on the civilian population from the very first day of the invasion. Germany was at war with Russia, France and Great Britain from 5 August 1914. Since Great Britain was supported by its Empire, what had begun as a regional conflict had by now been transformed into a world war within only a few days. The question of who was to blame for the war – whether Germany acted merely to forestall an attack by other powers or was indeed on a “quest for world power”, or whether poor crisis management meant that all sides simply “slid into war” – remains a matter of intense controversy.