Three line divisions, comprising seven infantry regiments were responsible for the immediate defence of the ridge. The paper strength of each division was approximately 15,000 men but their actual strength was significantly fewer. In 1917, a full-strength German rifle company consisted of 264 men; at Vimy Ridge, each rifle company contained approximately 150 men. Each German regiment held a zone approximately wide as far back as the rear area. When the Canadian Corps attacked, each German company faced two or more battalions of approximately 1,000 men each. Reserve divisions were kept about back instead of assembling close behind the second line according to the defence-in-depth theory.