Decision for war.

Decision for war.

In the immediate aftermath of the assassination on 28 June of Austrian Archduke Franz Ferdinand (the heir to the Habsburg throne) in the Bosnian capital, Sarajevo, the British newspapers denounced the Serbian nationalist assassin, Gavrilo Princip, and were generally sympathetic to the Austro-Hungarian monarchy. The newspapers blamed the Kingdom of Serbia for the crime, with rhetoric against "fanatics", "dangerous forces" and "reckless agitators". These responses were broadly shared across the political spectrum, with Liberal and Conservative papers expressing their shock and dismay. But by 27 July, press opinion had turned against Austria-Hungary. The national press divided along party lines, with Conservative papers stressing the obligation to support France, while Liberal papers insisted Britain had no such commitment and should remain neutral.

As Germany and Russia became the central players in the crisis (respectively backing Austria-Hungary and Serbia), British leaders increasingly had a sense of commitment to defending France. First, if Germany again conquered France, as had happened in the Franco-Prussian War of 1870, it would become a major threat to British economic, political and cultural interests. Second, partisanship was involved.

The Liberal Party was identified with internationalism and free trade, and with opposition to jingoism and warfare. By contrast, the Conservative Party was identified as the party of nationalism and patriotism; Britons expected it "to show capacity in running a war."Liberal voters initially demanded peace, but were outraged when the Germans treated Belgian neutrality as a worthless "scrap of paper" (the words of German Chancellor Theobald von Bethmann Hollweg in ridiculing the Treaty of London).

Germany, as part of a massive attack on France, invaded northern France through Belgium early on the morning of 4 August. The Belgians called upon Britain for military assistance under the 1839 treaty, and in response London gave Berlin an ultimatum which expired at 11 pm London time, which was ignored. King George V then declared war on Germany that evening.

Before war was declared, the British newspapers gave the crisis extensive coverage but varied wildly in recommended policy options, basically covering the entire spectrum from peace to war. C. P. Scott and the Manchester Guardian maintained an intense campaign against war. It denounced a "conspiracy to drag us into a war against England’s interests", arguing that it would amount to a "crime against Europe", and warning that it would "throw away the accumulated progress of half a century".  

The politician David Lloyd George told Scott on Tuesday 4 August 1914, "Up until last Sunday only two members of the Cabinet had been in favour of our intervention in the war, but the violation of Belgian territory had completely altered the situation". 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.

Once war was declared, defence of Belgium rather than France was the public reason given for the war. Propaganda posters emphasised that Britain was required to safeguard Belgium's neutrality under the 1839 Treaty of London.

As late as 1 August 1914, the great majority of Liberals—both voters and cabinet members—strongly opposed going to war. The German invasion of Belgium was such an outrageous violation of international rights that the Liberal Party agreed for war on 4 August. Historian Zara Steiner says:

The public mood did change. Belgium proved to be a catalyst which unleashed the many emotions, rationalizations, and glorifications of war which had long been part of the British climate of opinion. Having a moral cause, all the latent anti-German feelings, fueled by years of naval rivalry and assumed enmity, rose to the surface. The 'scrap of paper' proved decisive both in maintaining the unity of the government and then in providing a focal point for public feeling.

The Liberals succeeded in mending their deep divisions over military action. Unless the Liberal government acted decisively against the German invasion of France, its top leaders including Prime Minister H. H. Asquith, Foreign Minister Edward Grey, First Lord of the Admiralty Winston Churchill and others would resign, leading to a risk that the much more pro-war Conservative Party might form a government. Mistreatment of Belgium was not itself a fundamental cause of British entry into the war, but it was used extensively as a justification in wartime propaganda to motivate the British people.

The German high command was aware that entering Belgium could trigger British intervention but decided the risk was acceptable; they expected it to be a short war, and their ambassador in London claimed civil war in Ireland would prevent Britain from assisting France.

Historians looking at the July Crisis typically conclude that Grey:

was not a great Foreign Secretary but an honest, reticent, punctilious English gentleman... He exhibited a judicious understanding of European affairs, a firm control of his staff, and a suppleness and tact in diplomacy, but he had no boldness, no imagination, no ability to command men and events. [Regarding the war] He pursued a cautious, moderate policy, one that not only fitted his temperament, but also reflected the deep split in the Cabinet, in the Liberal party, and in public opinion.

The majority of the Labour Party, which as a member of the Second International had opposed the war, also shifted to support after the German invasion of Belgium with the exception of some members such as its secretary Ramsay MacDonald. The rest of the Labour Party leadership under Arthur Henderson calculated that the war would be brief and that opposing it would cost the party at the next general election.