United Kingdom declaration of war upon Germany (1914)

The United Kingdom declaration of war upon Germany occurred on 4 August 1914. The declaration was a result of German refusal to remove troops from neutral Belgium. In 1839, the United Kingdom of Great Britain and Ireland, France, and Prussia (the largest predecessor of the German Empire) had signed the Treaty of London which guaranteed Belgium's sovereignty.^[1][2]

However, the actual reasoning had at least as much to do with the British fright that lack of their help leading to a possible defeat of France could lead to German hegemony in Western Europe, with Christopher Clark pointing out that the British cabinet decided, on 29 July 1914, that being a signatory to the 1839 treaty guaranteeing Belgium's frontiers did not obligate it to oppose a German invasion of Belgium with military force.^[3] According to Isabel V. Hull:

Annika Mombauer correctly sums up the current historiography: "Few historians would still maintain that the 'rape of Belgium' was the real motive for Britain's declaration of war on Germany." Instead, the role of Belgian neutrality is variously interpreted as an excuse used to mobilise public opinion, to provide embarrassed radicals in the cabinet with the justification for abandoning the principal of pacifism and thus staying in office, or - in the more conspiratorial versions - as cover for naked imperial interests. ^[4]

Refer to British entry into World War I for further details.

At the time, the British government in London was responsible for the foreign affairs not only of the British colonies and protectorates but also of the five Dominions, so its declaration of war was made on behalf of the whole British Empire.^[5]