The fourth of Trevor Dupuy’s Timeless Verities of Combat is:
Flank and rear attack is more likely to succeed than frontal attack.
From Understanding War (1987):
Flank or rear attack is more likely to succeed than frontal attack. Among the many reasons for this are the following: there is greater opportunity for surprise by the attacker; the defender cannot be strong everywhere at once, and the front is the easiest focus for defensive effort; and the morale of the defender tends to be shaken when the danger of encirclement is evident. Again, historical examples are numerous, beginning with Hannibal’s tactical plans and brilliant executions of the Battles of Lake Trasimene and Cannae. Any impression that the concept of envelopment or of a “strategy of indirect approach” has arisen either from the introduction of modern weapons of war, or from the ruminations of recent writers on military affairs, is a grave misperception of history and underestimates earlier military thinkers.
“Seek the flanks” has been a military adage since antiquity, but its significance was enhanced tremendously when the conoidal bullet of the breech-loading, rifled musket revolutionized warfare in the mid-nineteenth century. This led Moltke to his 1867 observation that the increased deadliness of firepower demanded that the strategic offensive be coupled with tactical defensive, an idea that depended upon strategic envelopment for its accomplishment. This was a basic element of Moltke‘s strategy in the 1870 campaign in France. Its tactical manifestations took place at Metz and Sedan; both instances in which the Germans took up defensive positions across the French line of communications to Paris, and the French commanders, forced to attack, were defeated.
The essential emphasis of modern tactics and operational art remains enabling flank or rear attacks on enemy forces in order to obtain decisive results in combat. Will this remain true in the future? The ongoing historical pattern of ground forces dispersing on the battlefield in response to the increasing lethality of weapons seems likely to enhance the steadily increasing non-linear and non-contiguous character of modern battles in both conventional and irregular warfare.
The architects of the U.S. multi-domain battle and operations doctrine seem to anticipate this. Highly dispersed and distributed future battlefields are likely to offer constant, multiple opportunities (and risks) for flank and rear attacks. They are also likely to scramble current efforts to shape and map future battlefield geometry and architecture.
One of the significant selling points of military gadfly Douglas Macgregor’s proposed Reconnaissance Strike Group force structure is the capability for conducting continuous 360-degree combat operations.
Curiously enough however, current U.S. Army operational doctrine has little to say about the non-linear or non-contiguous aspects of battle. On the other hand, the current U.S. joint operations doctrinal manual has an entire section defining and describing linear and nonlinear operations.