Swarming (military)
Swarming in history: Enthusiasts of swarming sometimes apply it to situations that have superficial similarities, but really do not qualify as swarms. While swarms do converge on a target, not every military action, where multiple units attacked from all sides of a target, constitute swarming.  Other conflicts, especially historical ones, fit a swarming paradigm, but the commanders involved did not use the concept. Nevertheless, historical examples help illustrate what modern analysts do and do not consider swarming.
Some historical examples with at least some aspect of swarming include:

Siege of Samarkand: At the siege of Samarkand, Spitamenes used Bactrian horse archers in effective swarming attacks against a relief column sent by Alexander the Great. Bactrian horse archers surrounded various Macedonian phalanxes, staying out of range of their melee weapons, and shot arrows until they had no more. The archers would then withdraw to a supply point, but another swarm of horse archers would sometimes replace them, and sometimes attack elsewhere. The Bactrians eventually caused the phalanx to break formation, and destroyed it. Alexander recognized his forces could not directly combat horse archers, but that the horse archers needed resupply of provisions, horses, and arrows. Alexander split his forces into five columns and began building fortifications in the areas where the Bactrians had resupplied. Eventually, his anti-swarm tactics worked: cut off from resupply, the Bactrians had to meet the Macedonian phalanx, which were vastly superior in melee. Alexander made it priority to engage guerillas or other light mobile forces. Spitamenes was effective as long as his force were mobile, and he had adequate communications with mounted couriers. Once he was forced into direct battle with heavy forces, he lost the advantages of his forces and was defeated quickly. At the Battle of the Jaxartes River, Alexander once again faced swarming tactics from an army of Scythian horse archers. Alexander sent a unit of heavy cavalry ahead of his main line. As expected, the Scythian horsemen surrounded the detached cavalry. At the right moment, Alexander's cavalry reversed direction and pushed half of the Scythians straight into the main phalanx of Alexander's army, where they were slaughtered. Upon seeing this, the remaining half of the Scythian army retreated from the battle.

Mongols Horde: Mongols under Genghis Khan practiced an equivalent of swarming, partially because their communications, which used flags, horns, and couriers, were advanced for the time. Also one of the standard tactics of Mongol military was the commonly practiced feigned retreat to break enemy formations and to lure small enemy groups away from larger groups and defended positions for ambush and counterattack. Genghis Khan used the Yam system, which established a rear line of points for supplies and for remounts of fast-moving couriers. The remount system allowed horsemen to move much faster than the couriers of opponents without them. These couriers kept the Mongol senior and subordinate commanders informed, such that they could make fast decisions based on current information. In modern terms, the courier system provided the means of getting inside the opponent's OODA loop. With fast communications, the Mongols could make decisions not just on what they could see locally, but with that information oriented within the overall situation. They could then decide and act while the enemy were still waiting for information. Outnumbered Mongols could beat larger forces by faster communications, which allowed units to withdraw and regroup while other groups continually stung the enemy, withdrew in turn, while the earlier group again hit the enemy.

The evolution of modern swarming: Swarming was present in the operations of Alexander the Great and Genghis Khan, but were generally replaced by melee and mass in the pre-industrial era. More synchronized manoeuvre was paced by the availability of mobile communications. Blitzkrieg was certainly a use of manoeuvre, but it was less flexible than later operations in which every tank and aircraft had radios, and far less flexible than forces that have effective networked information systems. They define swarming, in a military context, as "...seemingly amorphous, but it is a deliberately structured, coordinated, strategic way to strike from all directions, by means of a sustainable pulsing of force and/or fire, close-in as well as from stand-off positions."
One aspect of swarming is that it moves away from the traditional model of a rigid chain of command. This paper suggests abandoning the term command and control  in favor of

agility: "... the critical capability that organizations need to meet the challenges of complexity and uncertainty"
focus: "provides the context and defines the purposes of the endeavor"
convergence. "convergence is the goal-seeking process that guides actions and effects."
Agility is a characteristic of an organization or unit capable of swarming. Focus can be designation of a goal by a higher-level commander, by a peer unit detecting a target, or by intelligence systems that feed information to the swarming units. Convergence is the key feature, which, while it can be distributed, causes swarming units to coordinate their actions, apply force, and know when to stop applying force.
Edwards holds that several axioms of military doctrine change with the use of swarming:

Osgood points out that swarming is not new, although the means of coordination and synchronization are going through significant changes.
Howard Rheingold cites mobile communications technology as a key enabler: The bees sense each other's buzzing and instinctually move in concert in real time. Text messaging on mobile devices and instantaneous file sharing off the internet via PDAs allows groups of people to receive their instructions, move in unison, nearly instantaneously, without prior planning or forethought. And, the technology allows groups to do so without a central leader. One modern example is the protesters at the World Trade Organization meetings in Seattle, in 1999, who were able to orchestrate their movement effectively in this way.

Modern military swarming: Current military applications of swarming combine the use of swarms: large numbers of relatively small agents or weapons, with synchronized actions, such that the swarm reacts faster than its opponent and defeats it. This section deals with general principles, but also high-intensity combat.
Swarming does not require good military intelligence alone, but intelligent soldiers who can manage multiple information streams and keep situational awareness. It is not advisable to have a soldier so engrossed in displays that an enemy can sneak up and hit him over the head with a rock. One of the challenges of designing modern networked systems is not to overwhelm the users with information. Those users will also need extensive training, with their sensing and synchronization information, to use them properly under combat stress.
Swarming requires autonomous or semi-autonomous operating agents, with strong synchronization and communications among them. Senior commanders release resources to the swarm, but do not control them once released. If the agents are semi-autonomous, there will be an on-scene commander giving general direction to the swarming agents.

A 1987 proposal: In the 1980s, the Soviets developed an 'Operational Maneuver Group' (OMG) for a fast armored thrust deep into NATO defences east of the Rhine River. An OMG was expected to exploit strategic surprise with a force equal or greater than an armored division, featuring up to 700 tanks, 500 IFVs, and a substantial number of helicopters. As a countermeasure, NATO considered neutron bombs but their use was politically controversial. NATO instead devised a plan to slow the thrust with a swarming counterattack, called Dynamic Density, which used single-seat Small Military Aircraft (SMAs) operating autonomously in pairs with infantry ATGWs such as Milan, their pilots being infantry. One aircraft would carry the Milan post and four missiles, the other the night-vision sight and four missiles (two of which might be anti-helicopter), and the tactics would be shoot and scoot. The SMA, known as the Dragoon, was evaluated and highly praised by the MoD's test pilots at Boscombe Down, its STOL performance and ease of handling making it ideal for this role. Large numbers would be needed and 5,000 was suggested as sufficient to ensure that swarming would be successful against a force as large as an OMG. Once it was recognized that success could be claimed with a significant deceleration, other novelties were introduced, among which was Synthetic Density which required the SMAs to distribute pneumatic models (fitted with radar reflectors) of tanks and artillery along the OMG's MLA, these requiring the room to be put down and time to be lost before progress could be resumed.
The proposal was published in the Journal of the Royal United Service Institution and a couple of years later a shorter article suggested that if the Soviets themselves had used SMAs in swarms in Afghanistan their COIN operations against the Mujaheddin would have been far more successful. Contemporary Western armies in Afghanistan can readily accept that swarming at the tactical and operational levels is appropriate, but the physical structure of the country rules out the currently available fighting vehicles. However, networked and swarming SMAs, again 5,000 in number, all armed with laser designators for the second echelon of conventional ground attack aircraft, would constitute force multipliers with a substantial impact.