Sea power

This was the underlying dynamic which explained Britain's entry to World War One. Formally speaking, Britain was not under any obligation to support France, let alone Russia, in a war with Germany.

Indeed, the first response of the foreign secretary, Sir Edward Grey, was to call on Germany to cooperate in convening a conference of the great powers. When Germany refused, Grey confronted the fact that imperial obligations and European policy were indivisible.

Politically, Britain could not afford to alienate either France or Russia, given its reliance on them for the system of global security which it had constructed. Strategically, its maritime power meant that it could not permit a mighty and hostile European power to dominate the Low Countries and so threaten the English Channel.

The implication was that Britain would wage war as a sea power.

Germany's invasion of Belgium became the mechanism by which such thoughts could be rendered in popular and more universal terms: great power politics were presented as ideologies.

The implication was that Britain would wage war as a sea power, which was exactly how Grey made his case to the House of Commons on 3 August 1914.

The French government was even more anxious to ensure that Britain honoured the Anglo-French naval agreement of 1912 - which had left the defence of France's northern coast in the hands of the Royal Navy - than to secure the despatch of a British Expeditionary Force to the continent.