The Fourth Army was formed on 5 February 1916 under the command of General Sir Henry Rawlinson to carry out the main British contribution to the Battle of the Somme.

The Fourth Army was formed in France on 5 February 1916, under the command of Sir Henry Rawlinson.

The plan for the Fourth Army during the Third Battle of Ypres (31 July – 10 November 1917), was to mount Operation Hush, an amphibious invasion of the Belgian coast.

Once the Germans had been pushed back from the Passchendaele–Westroosebeke ridge and an advance begun on Roeselare and Torhout, the XV Corps would mount the coastal operation.

The Fourth Army spearheaded the British Hundred Days offensive that began with the Battle of Amiens and ended with the Armistice in November, 1918.