The official reason given for Britain's declaration of war on 4 August 1914 was the German invasion of Belgium, which was intended to deliver a rapid knock-out blow against France. Britain had undertaken by the Treaty of London (1839) to guarantee Belgian neutrality. To a large extent, however, Belgium was the pretext to enable the Prime Minister, H.H. Asquith, and the Foreign Secretary, Sir Edward Grey, to persuade wavering members of the Cabinet to honour Britain's commitments to France. 1 The strange truth is that, although the British Government had no formal alliance with France, it considered that it was honour-bound to go to war on her behalf. This was the result of the gradual tightening up of relations between the two countries ever since the 1904 Anglo-French Entente. The scope of the agreement had initially been confined to resolving their disputes in Egypt and Morocco but this was gradually extended to a diplomatic undertaking to protect each other's interests; hence Britain had sided with France against Germany at the 1906 Algeciras Conference and over the Agadir Crisis in 1911. Britain had also geared her defensive response to an ever-increasing German threat by undertaking military and naval co-operation with France. By 1914 Britain was committed to defend the French coastline in the event of a German attack, in return for a French promise to defend the Mediterranean. Britain had also made preparations to despatch a British Expeditionary Force (BEF) to assist the French armies to repel a German attack. By 1914, therefore, a de facto alliance existed between Britain and France, although the precise nature of Britain's military obligations was to be defined more precisely after the actual outbreak of war.
This chapter will examine Britain's military role in the war, together with the political, social and economic impact of the war on Britain in the future. These themes will tie in with all the other chapters on the inter-war period.