As far as the British Army is concerned, the war can be considered to have been fought in three phases.

1. Preconceptions destroyed

Between the first encounter battle at Mons in August 1914 and the failed offensive in support of a larger French affair, at Loos in September 1915. Under the command of Sir John French, the BEF lost the core of the pre-war regular army while still being greatly outmanned and outgunned. It became clear that the enemy positions could be broken into, but not broken through, without the deployment of much larger forces.

2. The wearing-out fight

Between the Battles of the Somme, which started in July 1916, and the end of the German offensives in May 1918, under the command of Sir Douglas Haig. Characterised by the deployment of very large armies, engaged in attrition warfare. The Territorials and New Armies took the field in force. Casualties were very high, for comparatively small territorial gains. New technologies and tactics were tried.

3. Blow after Blow

From the launch of a surprise attack at Amiens in August 1918, until the Germans called for an Armistice in November 1918. Haig's British Army, battle-hardened and having learned the hardest way of all, pummelled the German foe in a great and almost continuous advance.