The Army The Army Corps The Division The Brigade The Battalion       The Army     The British Forces on the Western Front were divided into four or five armies. The British Army in the field was commanded by Field Marshal Sir Douglas Haig. Throughout the war the British Army varied in strength, but usually employed 4,000,000 (1917) soldiers in the field. The Canadian Corps belonged to the 1st British Army, but had stints with the 4th Army as well.         The Army Corps     An Army Corps consisted of a number of Infantry Divisions, depending on its needs. The Corps was commanded by a lieutenant general. Its numeric strength varied, but could put as many as 120,000 men in the field. The Canadian Corps was made up of four Divisions, all Canadian, but often had British Divisions attached for special attacks or battles.     The Division       The Infantry Division was composed of three Infantry Brigades and had 20,000 soldiers. It was commanded by a major general. The 20,000 soldiers included 12,000 infantry, 3,500 artillerymen, 750 in a medical section, and 2,000 engineers and pioneers.         The Brigade     The Infantry Brigade was commanded by a brigadier general and consisted of four battalions (4,000 infantrymen). Each brigade had engineers, signals, a field ambulance, a trench mortar unit and a machine-gun unit.     The Battalion       The Infantry Battalion consisted of 1,000 men. This was the theoretical strength of the unit; after headquarters staff, illness, wounded, etc. were deducted, a battalion would normally put 650 rifles into the line. Commanded by a lieutenant colonel, each battalion was made up of four companies (200 men), commanded by a major or captain. In turn, the company was broken into four platoons commanded by a lieutenant, and each platoon into four sections commanded by a sergeant.