Artillery was developed heavily and rapidly during the First World War, from a Napoleonic style direct-fire weapon employed in the front line, to a war-winning weapon, massed in great numbers far behind the lines and used scientifically to achieve great results. A wide variety of weapon types and sizes were employed during the 20th Century, most often in their own units.
The most basic distinction in artillery weapons was that between a gun, which fired projectiles at relatively low angles, and a howitzer, which was capable of firing at high angles, though the 25-pounder, which was a mainstay of artillery British beginning in 1939, was officially a gun-howitzer as it was capable of effective fire in both roles.
First World War
Horse Artillery - Light and mobile, the Horse Artillery used small 13-pounder guns.
Field Artillery - Field artillery formed the majority of the artillery and used both 18-pounder guns and 4.5-inch howitzers.
Siege Artillery - Used a variety of 6-inch, 8-inch and 9.2-inch guns, largely in counter-battery work or cutting wire entanglements in No Man's Land.
Heavy Artillery - Heavy Artillery and Garrison Artillery used the 60-pounder traditionally for guarding strongpoints; there was little distinction in trench warfare between their role and that of the siege artillery.
Anti-Aircraft Artillery - Developed as the war went on and the role of the airplane gained in importance.
Trench Mortars - Developed for trench warfare, Canada used the 3-inch Stokes, 6-inch Newton and 9.45-inch Newton weapons.
Second World War
Field Artillery - Canada started the war with 75-mm guns, 18-pounders and converted 18/25-pounders, until replaced in 1941 by the 25-pounder.
Self-Propelled Artillery - Beginning in 1943, purpose-built tank chassis carrying field guns, for use in armoured divisions, rather than the towed artillery of the infantry divisions. Canada used two types, the Sexton, mounting a 25-pounder gun on the Canadian Ram chassis, and the 105mm gun married to a Sherman chassis, known as the Priest. These were used by the 3rd Canadian Infantry Division for the D-Day assault and used in the opening weeks of the Normandy campaign, until the vehicles were replaced by towed 25-pounder guns, and the vehicles converted into Kangaroo armoured personnel carriers.
Medium Artillery - Canada began the war with 6-inch howitzers, replaced beginning in October 1941 with 5.5-inch gun-howitzers. Insufficient supply of 5.5-inch weapons meant that introduction of 4.5-inch gun-howitzers had to be made in Italy in February 1944. As the 4.5-inch weapons had greater range and accuracy, a number were retained to supplement the 5.5.
Anti-Tank Artillery - The 2-pounder gun was standard at the beginning of the war, and in January 1942 the decision was made to replace it with the 6-pounder gun in anti-tank regiments. The 17-pounder was developed to replace the 6-pounder, and towed equipment was used as well as self-propelled 17-pounder guns (on vehicles such as the M10 and the Archer) and the self-propelled 3-inch (76mm) M10.
Anti-Aircraft Artillery - Canada used the Bofors 40-mm anti-aircraft gun in the light role, and had a 3.7-inch heavy anti-aircraft gun. Both were occasionally used against ground targets, particularly as the fortunes of enemy air forces declined. A number of 20-mm guns were found in brigade support groups and armoured formations, but there was little need for its services against aircraft and its mount was unsuitable for use against ground targets and it was withdrawn from service in August 1944.
Field Regiment - 24 gun regiment (3 Batteries, each of 2 Troops of 4 guns)
Self-Propelled Regiment - 24 gun regiment (3 Batteries, each of 2 Troops of 4 guns)
Medium Artillery - 16 gun regiment
Anti-Tank Regiment - 18 gun regiment
Light Anti-Aircraft Regiment - 36 gun regiment (3 batteries, each of 12 guns, 2 equipped with 40mm Bofors, 1 equipped with 20mm)
Heavy Anti-Aircraft Regiment - 24 gun regiment