British infantry brigades of the First World War

The pre war regular army only had eighteen infantry brigades, with another forty-five serving with the reserve Territorial Force (TF).

Eventually, as the war progressed, a brigade had its own machine gun company and a trench mortar battery assigned.

It consisted of 247,432 regular troops organised into four Guards, 69 line infantry and 31 cavalry regiments, along with artillery and other support arms.

[2] The Special Reserve had another 64,000 men and was a form of part-time soldiering, similar to the Territorial Force.

Near the end of 1914, when regular army battalions returned to Europe from serving around the British Empire, they formed the 7th and 8th Division, with the 20th–25th brigades.

[12] At the start of the First World War French, Russian and German divisions consisted of two brigades each of which were made up of two regiments.

[14][15] Over the course of the war, the composition of the infantry brigades gradually changed, and there was an increased emphasis upon providing them with their own organic fire support.

[16] Brigades that served in the Mesopotamia Campaign had their own supply and transport columns of the Army Service Corps.

[18] In the trench warfare on the Western Front, an infantry brigade's defensive responsibilities depended upon where they were at the time.

On 21 March 1918, the first day of the German spring offensive, the 173rd Brigade was responsible for 5,000 yards (4,600 m) of the front line.

[20] The thirty-six brigades, twelve divisions, of the Fifth Army possibly had the hardest task with 42 miles (68 km) of front to defend.

[21] Within the brigade a typical deployment was one battalion in the front line, with the other two in reserve, about 2 to 3 miles (3.2 to 4.8 km) back.