The armies of the combatants were organized into Corps, Divisions, Brigades, Battalions, Platoons.
For example, the Canadian Army was called the Canadians Corps. The commander of the Canadian Corps in Europe, in 1917 was Lieutenant-General Hon. Sir Julian Byng. All “his” forces were organized as outlined on this link: Order of Battle – Vimy Ridge
When you are researching various Battalions and / or veterans on the Strathroy cenotaph, you may refer to this page to see “where they fit in to the big picture”.