Defeat in detail

Defeat in detail is a military phrase referring to the tactic of bringing a large portion of one's own force to bear on small enemy units in sequence, rather than engaging the bulk of the enemy force all at once. This exposes one's own units to a small risk, yet allows for the eventual destruction of an entire enemy force.

One definition states: “Defeat in detail is a doctrinal military term that means to defeat an enemy by destroying small portions of its armies instead of engaging its entire strength."

Premise
In military strategy and tactics, a recurring theme is that units are strengthened by proximity to supporting units. Nearby units can fire on an attacker's flank, lend indirect fire support such as artillery, or maneuver to counterattack. Defeat in detail is the tactic of exploiting failures of an enemy force to coordinate and support the various smaller units which make up the force. An overwhelming attack on one defending sub-unit minimizes casualties on the attacking side, and can be repeated a number of times against the defending subunits until all are eliminated.

An attacker can successfully "defeat in detail" by exploiting a) absolute weaknesses or comparative disadvantages in the deployment or structure of defending troops and/or b) advantages, such as maneuvering speed, that the defender cannot match. Chief among examples of a) is the case of asymmetric support structure, in which unit A can support B but unit B cannot support unit A. For example, during World War I, when horse cavalry were still in use to some extent, aircraft could support cavalry, but cavalry had little or no ability to support aircraft.  Thus, if a unit is equally suited for use against cavalry and against aircraft, using it to eliminate enemy aircraft would have benefits lasting well into future engagements against enemy cavalry units weaker for their lack of support, but using it against enemy cavalry—and thereby leaving the enemy aircraft intact for subsequent engagements—would bring benefits during that engagement alone.

Weaknesses of defenders
Examples of weaknesses in the deployment or structure of defending troops would include:
 * Dug-in units spread out over so wide a distance that the maximum effective range of their weapons is significantly smaller than the distance between units, preventing those units from supporting the flanks of neighboring units.
 * Defending units on opposite sides of physical barriers such as hills, forests or rivers.
 * Defending units whose artillery support is too far to the rear, and thus cannot effectively engage attackers.
 * Defending units which have no effective communications with their command structure, and thus cannot request assistance.

Enabling methods
Methods which can be used to enable the attacker to defeat the enemy in detail include:
 * Attacking one unit faster than other defending units can move to counter-attack.
 * Attacking faster than the defending intelligence, communications, command and/or control systems can respond to (see OODA loop).
 * Disabling and/or disrupting systems required for one defending unit to support another (as by attacking, e.g., communications, command, and/or control systems with, e.g., air strikes, artillery attacks, and/or radio jamming).

Strategic campaigns

 * 1792-1797: Napoleon Bonaparte's first campaign in Italy during the French Revolution, in which the French army of 37,000 men defeated 52,000 Piedmontese and Habsburg troops with rapid advances that prevented the two nations' armies from combining.
 * 1862: Stonewall Jackson's Shenandoah Valley campaign, in which Jackson defeated three Union commands (a combined 60,000 men) with his own command (17,000 men), by fighting each of the enemy columns in turn while the Union commands were separated from each other by impassable terrain or significant distance.
 * 1912-3: The Balkan League's victory over the Ottoman Empire in the First Balkan War.
 * 1914: The battles of Tannenberg and Masurian Lakes, where the Germans exploited the local topography and the personal antipathy between the Russian commanders to defeat the Russian Second Army and then the Russian First Army in sequence.
 * 1941: Operation Compass, when the British defeated an Italian force more than four times their own size in North Africa by exploiting the fact that the Italian defenses could not mutually support each other.

Tactical examples

 * Gallic tribes tried and nearly succeeded in defeating Caesar's army in detail at the Battle of the Sabis.
 * Battle of Raate Road in Finland (1940)