War strategy: Divide and. . ."conquer?"

I’ve read about this many, many times: Some army penetrates another army’s ranks, thus dividing them. Mayhem ensues, and the attackers get the upper hand.

Why? It would seem to me as though the attackers are now surrounded by the enemy, making for easy pickin’s. Where is the flaw in this reasoning (since, apparently, it is good strategy)?

It’s not so much a plan for attack on the battlefield as it is a strategy to employ before the battle. The idea being if you can force your opponent to have to split up or divide his forces, say, in response to a diversionary raid or something, you’ll have to fight less troops when you do get in battle. The phrase has also been used in reference to alliances between nations. If you can cause a division between your opponents and their friends, you might not have to fight so many people.

There are a few issues that need to be worked out.

Divide and Conquer is not always a battlefield tactic as you have explained above. Rather it is a general strategy, in which the attacker prevents concerted resistance by political maneuvering or a series of field encounters designed to stop enemies from joining together in opposition. For example, the British used this strategy in India, whereby they were able to coax, bribe, and threaten Indian princely states into submission one by one, exploiting disunity and keeping the Indian rulers divided.

As a battlefield tactic, its effectiveness are much more limited. But I trust I have already answered your question, so I will spare you a tedious discussion of ancient warfare.


If you surround the enemy, you plan the division of your resources. If you are forced to divide, you cannot plan how your resources are divided.

A tactic put to good use by Crotes, the conqueror of mexico. with a couple of hundred Spaniards he conquered the Mexican empire. of course, those who have not read the history will tell you stories about how the Mexicans were terrified by horses and firearms.

The truth is Cortes was a shrewd politician and turned some of the tribes subject to the mexicans against them. Most of the the war was not fought by Spaniards but by indians. And when the Spaniards fought they were just as subject to slaughter.

Cortés divided his enemy to conquer it but the expression does not refer to the battlefield.

mjollnir writes:

Two (among many) reasons
[li]We can’t turn left (or right) in a reasonable amount of time; we foul each other’s sarissae, and whilst we’re trying to get them straightened out, the legions work a fearful slaughter (actually happened at Cynoscephalae)[/li][li]Good idea; we’ll just wheel around and shoot those mother…oops, out of ammo. Hey, looey, get on the field phone and call the transport battalion…err, yeah, that one that the enemy just overran[/li][/list=1]
Those are basically the conditions that manuever warfare works: when the enemy is equipped (disposed, etc.) so that he can’t respond to a flank attack fast enough, or when the troops can penetrate the enemy’s line of fighters, and wreak havoc amongst the now relatively helpless logistic and headquarters troops (there’s more to fighting wars than pulling a trigger, or even thrusting with a gladius).

Landsknecht and Maeglin are correct that the phrase “divide and conquer” is generaly applied to diplomatic and political stratgy than to military tactics.

It can also be a battlefield tactic when one enemy has relatively little mobility or two sides are not communicating well. For example, at the battle of Second Bull Run, Lee’s Army of Northern Virginia coaxed Pope’s Army of Virginia into an attack; Pope expected that McClellan’s Army of the Potomac to support him, only to find that McClellan considered his troops to weary and demoralized to make the march. Rather than outnumbering the Rebs, Pope was actually outnumbered, and his army was nearly destroyed. Likewise, McClellan had taken a serious beating previously during the Seven Days Campaign because he had to cross several rivers, often leaving himself with his army divided up (and thus ripe candidates for the Army of NV to pounce upon and destroy any one part without incurring many casualties upon themselves).

But, in general, it is more often used as a ‘general strategy’ than as a battlefield plan, in the sense of getting a group of enemies that would be unconquerable in unison to focus upon their personal differences, individual weaknesses, etc., and then destroy each individual unit/army/country one by one, and thus eliminate a foe that was, in theory, much stronger than you. Take a look as well at Napoleon’s early campaigns, where he worked hard to get the anti-French alliance of Prussia, Russia, and Austria to fight France individually (and thus get whomped) rather than all at once (which, once they finally did, allowed them to whomp France).

Essentially, the reason is that once you’ve broken an army’s line, you’ve more or less broken the army.

The short answer is that a field army is really, really complicated. Even a small army with few supporting arms is a hideously complex organization. Moving it around in the field and ordering its subcomponents to do this and that requires a very high level of organizational skill.

Armies are like a giant game of rock-paper scissors; every component of an army is necessary to make the army an effective combat force. Losing any part of it cripples the army. All the tanks on earth will not help you without infantry support; all the infantry in the world will not help you without armor. An army without artillery can be hammered relentlessly from a distance without fear of returned fire. An army with all the combat power in the world but no recon or effective EW is blind and will blunder into something that will kill it. An army without enough trucks will bog down. An army with no air support - well, ask the Iraqis, or the Germans in 1944 France, how much they enjoyed incessant aerial bombardment. And so on.

Consequently, an army in the field is very carefully arranged when prepared for battle, in accordance with the fundamental principles of mechanized warfare.

If the Rickjayian 1st Infantry Division were arrayed to face the attacking Mjollnirir 1st Tank Corps, it wouldn’t just slap guys with guns around something to defend. In front of the forward line you’re have a screening force of mobile recon units. The forward line would comprise maybe six infantry battalions, carefully placed in positions that provide cover but allow a planned arc of fire in front of them. Anti-tank weapons are placed in specific spots to cover “kill zones,” areas I predict your tanks will go in an effort to break through. Behind the forward line I’ll have more infantry battalions in reserve; if I have tanks I’ll keep them here so I can use my reserve to plug holes. Artillery groups will be placed behind lines so that all approaches can be covered. Positions must be found for my electronic warfare installations so I can use DF and intercept to hear you coming and know where you are, an so my jamming detachments can jam your radios. I need to place my headquarters and set up communications links. A place must be found for logistics points, field hospitals, kitchens, and the like. I’ll have step-back positions to pull my army back to so I can quickly prepare another defensive line if a breakthrough seems likely.

If you break through, all that goes to hell. My infantry battalions are out of position now; I could have thousands of guys ready to fight but in the wrong place, and hustling them to the right place in the panic and confusion will be night on impossible. Your tanks will overrun my logistics points, my field hospitals, even my HQ. My direction finders are useless if they’re not lined up right. My jammers will jam my own radios if they try to jam yours. My artillery is completely useless and vulnerable to destruction. All my communications links will be lost.

You’re surrounded by my army now, but you’re surrounded by a disorganized mob running pell-mell rather than a division properly entrenched and ready to take you on. A disorganized army is pretty much dead meat.

I agree that “divide and conquer” is largely a diplomatic/political term. However, it has a close military cousin: defeat in detail. This is the destruction of one or more enemies by bringing a superior force to bear upon unsupported, separated units.

One of the finest (and perhaps luckiest) examples of defeat in detail is that of Frederick the Great in the Seven Years’ war. Frederick used Prussia’s interior lines to march to his western border and defeat an approaching French army, then wheeled his small but elite army, countermarched, and confronted an advancing Russian army. Both attackers had a numerical advantage over Frederick, and had they been allowed to unite, things likely would have been very different. (Supposedly, the French and Russians had agreed on a specific date to attack, but neither had taken into account the difference in their calendars. I doubt this, but it makes a great footnote.)

Soliers in the field absolutely hate having an enemy in their rear. It only makes sense–you want to face your enemy, and if you have enemies in multiple directions, you start to get nervous. The presence of even a few of the enemy behind an old-fashioned line of battle was often enough to swing the moral initiative to the attacker who infiltrated or outflanked.

That having been said, history is also replete with examples of surrounded or threatened armies that did not lose nerve. Winifield Scott simply ignored the danger of an enemy force appearing in his rear and boldly advanced to Mexico City. During the Crimean War, a small British unit found itself cut off by an advancing Russian column, so the soldiers fixed bayonets and fought their way through the Russian column in order to rejoin the parent unit. The successful British defense (before Monty’s counteoffensive) before Alamein was actually designed to allow for some German penetration into the British lines–into carefully selected “kill zones.” And most commendable of all, the Marines around Chosin Reservoir simply “attacked in another direction” when bisected and surrounded by a million Chinese. The separated units attacked toward each other, effected a junction, and then fought their way back to the sea.

You might want to check out an account of Hannibal Barca’s battle strategy at Cannae aginst the Romans. Greatly outnumbered, Hannibal’s army succeeded in all but destroying the Roman army by allowing the Romans to attack his weak centre and, thus, enabling him to outflank and encircle the Romans.


A good example of “defeat in detail” in more modern warfare would be the German blitzkrieg, especially against France and the first few months in Russia.