Major John N. Rickard, CD, PhD

Clausewitz’s belief that the defense was inherently stronger than the offense as a form of war helped perpetuate the long-held 3:1 ratio as a virtual principle of war.  The origin of the 3:1 rule can probably be traced to the Franco-Prussian War. The concept rested on the belief that an attacker required a numerical superiority of 3:1 to achieve a breakthrough of a linear defence. These metric problems are only compounded by an almost slavish adherence by military historians to the 3:1 rule. Indeed, Shelford Bidwell and Dominick Graham have argued that 4:1 was the minimal force ratio required to achieve a break in at the point of contact.  F.O. Miksche observed that executing a successful break-in battle against a prepared defense (Main Defence Area (MDA) required four things to succeed, surprise and speed (forming manoeuvre) and material superiority expressed in the form of firepower (or systems delivering it) Blitzkrieg.  Miksche, however, did not mention numerical superiority. The 3:1 concept is a ‘law’ perhaps only at the tactical level and even less a law at the operational level. It did not hold at all at the strategic level during the war. It fell apart completely in France in 1940. The Germans invaded France in 1940 with 135 divisions against 151 divisions and 2,439 tanks against 4,204.  It is well to recall also Lieutenant-General Sir Richard O’Connor’s victory over the 100,000 man Italian Tenth Army with the 30,000-man Western Desert Force during Operation COMPASS.

There is evidence from Italy during the Second World War that 3:1 was used as a planning assumption. General Sir Harold Alexander declared “it is generally agreed, a superiority of at least three to one is required for successful offensive operations.”  Alexander was probably influenced by his Chief of Staff, John Harding. In his appreciation he declared that the army group required at least a 3:1 superiority wherever Alexander decided to strike a main blow. 

Some degree of numerical superiority is necessary if we accept that it takes less force to defend the same frontage as it does to overcome it.  Indeed, we all understand that the ground dictated how much of our available superiority was actually deployable against the Germans. As a study of New Zealand operations against Cassino noted, “it was never possible to make full use of our superiority in numbers owing to the nature of the ground.”