The Personal Defense Weapon (PDW) is a relatively new type of firearm that has become available to the world's armed forces over the course of the last 25 years. As the name implies, the PDW was originally intended as a purely defensive weapon. Its characteristics made it ideal for a military's support personnel not typically engaged in frontline combat (e.g., medics or technicians). In recent years, however, PDWs have taken on a primarily offensive role, specifically in the fields of law enforcement and special operations. To fully understand this change in thought, one must understand the innovations in military philosophy over the last few decades.

Background: Generational Warfare and Military Philosophy

In 1989, the United States military establishment undertook a semi-comprehensive assessment of the history of warfare up to that point and divided the prior 400 years or so into what were termed "generations" of warfare. The first generation was typified by states creating standing armies that fought one another in fairly static, standardized columns of large groups of soldiers (for example, the Napoleonic Wars or the American Revolution). The second generation also featured massed armies but also saw the advent of smaller units of fighting men simultaneously trying to achieve military objectives outside of the larger mass of forces using technologically advanced weaponry (the American Civil War or World War I). The third generation was ushered in by Germany's innovative blitzkrieg (literally, "lightning war") tactic that called for massive and overwhelming movement at an inconceivably fast rate to the enemy's rear, thus cutting off supply routes and encircling the foe. The fourth generation is typified by states struggling against non-state actors (i.e. terrorists) across national boundaries with all available non-militarized resources (e.g. media, hacking, psychological warfare, international law, etc.) and includes urban warfare. According to this philosophy, the conflicts of the world today are generally lumped into the "fourth generation" category, at least by the standards of the U.S. military.

Submachine Guns and Assault Rifles

Accompanying each generation of warfare (if one accepts the terminology, which is not without controversy) is a different range of weaponry. During World War II, the German Wehrmacht created what is essentially the standard by which units in most of the world's armed forces are organized today. The individual unit was centered around the heavy machine gunner, who carried a selective-fire weapon capable of firing what is considered a "full sized" rifle round at high rates of speed (typified by the MG 42, which fires at a rate close to 1500 rounds per minute, rendering the human ear unable to differentiate between individual shots). The NCO in charge of the unit typically only carried a pistol and the other members were armed with bolt-action rifles (likely firing the same round as the machine gunner) and submachine guns (SMGs, fully-automatic weapons firing a smaller, pistol-caliber round) and filled supportive roles, both offensive and defensive. As an illustrative example, in the German context, machine gunners used MG 42s (7.92x57mm), riflemen had Mauser Karabiner 98ks (using the same round as the MG 42 to promote interchangeability), sub-machine gunners had MP 40s (9x19mm, the same bullet that is generally just called "9mm" today), and the NCO had either a Luger P08 or Walther P38 that used the same 9mm round.

In most modern militaries the same general idea still applies, although obviously frontline soldiers do not generally use bolt-action rifles incapable of semi-automatic or fully automatic fire. Instead, the roles of the rifleman and the sub-machinegunner have been combined and the primary weapon of choice is the assault rifle. Assault rifles differ from standard rifles in that they fire smaller rounds than the aforementioned full sized weapons such as the MG 42 or the K98k. Again, the Germans created the concept of the assault rifle during World War II, releasing a fully-automatic weapon that bridged the gap between machine guns and sub-machine guns. This weapon, called the Sturmgewehr (literally "assault rifle") fired a 7.92x33mm round that had the same penetrative and explosive effect of the larger round but at a shorter distance and with more controllability by the user in fully automatic mode. While the MG 42 usually had to be mounted on a complex tripod and supported by a group of nine other men, a Sturmgewehr could be fired from the shoulder and easily carried and used by anybody. Many experts believe that the relatively small supply of Sturmgewehr weapons and ammunition was one of the few things keeping the Nazis from winning World War II.

The first mass-produced assault rifle was the famous AK-47 developed by the USSR. The AK-47 is similar in many regards to the Sturmgewehr, both in its method of operation and its outside appearance (likely because one of the designers of the weapon was captured and forced to work in the Soviet Union after the war), but it was significantly cheaper and easier to produce than its predecessor. The AK-47 fires a 7.62x39mm round, and while not horrifically accurate at longer distances, it is almost indestructible and enjoys a decently high rate of fire. The AK style rifle is ubiquitous to the point that conservative estimates say that nearly 20% of all firearms currently in existence are AK-pattern rifles. They are so common that in certain parts of Africa, AKs can be purchased for the equivalent of roughly $6 (six U.S. dollars). After experiencing the devastating effects of the AK-47 in the Vietnam War when matched against older weapons such as the M1 Garand or the M14, the United States in the 1960s adopted the AR-15 as its primary infantry rifle and called it the M16. The M16 fires what is called a Small Caliber, High Velocity (SCHV) bullet, namely the 5.56x45mm round. While the 5.56 round does not cause the same level of damage as the 7.62 bullet, it is more accurate over longer distances and weighs significantly less, allowing individual soldiers to carry more ammunition than if they were carrying equivalent AK rounds. Seeing the utility and effectiveness of the SCHV concept, the Soviets engineered the 5.45x39mm round in 1974 to replace the heavier and less accurate 7.62 bullet in 1974 for use in their new AK-74 assault rifles; China followed suit in the 1980s with the 5.8x41mm round. Assault rifles like the M16 or the AK are generally around one meter in overall length and are meant for engagements within 300 meters, although they usually have effective ranges of about twice that distance.

The First Personal Defense Weapons

While this might seem to be extremely unnecessary background information, all of this is important to understanding the development of the PDW as well as its defining characteristics. The PDW exists in a somewhat nebulous area between the SMG and the assault rifle, and there is a certain amount of overlap between the three groups, prompting some to dismiss the PDW label and categorize individual weapons as either SMGs or assault rifles. Generally speaking, Personal Defense Weapons are compact, lightweight, selective-fire, and often chambered in either experimental or proprietary calibers that are halfway between pistol cartridges and assault rifle rounds. Other common features include short barrels and retractable or collapsible buttstocks. The first PDWs were basically more compact SMGs, which makes sense when you consider that SMGs like the Tommy gun or the aforementioned MP 40 are about as big as standard carbine-sized rifles and were originally meant to be used in a close-range offensive context. The ideal PDW is one that can be easily stowed in an armored vehicle and quickly reached and readied in the event of an emergency. PDWs theoretically should also be easily and comfortably fired with either a one or two handed grip. Generally speaking, PDWs are about half to two-thirds the overall length of comparable assault rifles. The effective range of most PDWs is less than 200 meters.

The first PDW really worth mentioning was the Czechoslovakian vzor 61, commonly known as the Skorpion (the meaning of the name should be somewhat obvious). The Skorpion fired the 7.65x17mm round, also called the .32 ACP. It was designed in 1959 and entered service in 1961, hence the vzor 61 designation (literally "model 1961"). The Skorpion features a top-folding stock and is not much larger than many normal pistols. It is, however, capable of fully automatic fire at a rate of roughly 800 rounds per minute (for reference, emptying the gun's 20-round magazine would take less than 3 seconds if the trigger was simply depressed until empty). It is still in use in both the Czech Republic and Slovakia mainly by special forces groups and has been licensed for production in other countries for the same purpose.

The next important pistol-caliber PDW was the famous MAC-10, an American weapon produced in both 9mm and .45 ACP variants. It is roughly the same size as the Skorpion but with a significantly higher rate of fire (approximately 1000-1100 rounds per minute) and more maneuverability owing to the fact that the magazine is stored in the pistol grip rather than in front of it like its predecessor. Officially, it was issued during the Vietnam War to special forces teams sent behind enemy lines. Because of its simple design and relatively small production cost, it is one of the most copied and most utilized weapons throughout the world, both by state militaries and non-state actors.

Modern Personal Defense Weapons and Changing Applications

In the 1980s and 1990s, a general trend toward downsizing both bullets and their cartridges resulted in the development of specific PDW calibers. This trend was due in large part to the advent of the above mentioned fourth generation warfare, which centered around relatively small units quickly accomplishing their objectives at fairly short ranges. The modern American military philosophy is called "rapid dominance," which is perhaps a more politically correct way of saying "blitzkrieg." In traditional military tactics, the main mass of infantry would be the spearhead of the assault, augemented by heavy artillery and air support if possible. The opposite is true today, with artillery and air power representing the main offensive thrust and being supported by decentralized infantry units engaged in closer range mop up operations. While the assault rifle would still continue to be the standard-issue infantry weapon, the intermediary PDWs took on an increased offensive importance with the advent of serious urban warfare (even to the point of fighting room-by-room in individual buildings).

One of the best examples of an effective PDW is the Belgian-made Fabrique Nationale P90. Designed throughout the late 1980s and introduced in 1990, the FN P90 was engineered around an experimental 5.7x28mm round. While the casing was longer than that of the standard NATO 9x19mm pistol cartridge (storing more powder and thus allowing it to travel farther), it used a bullet dimensionally similar in most respects to the 5.56x45mm SCHV assault rifle round. The result was a similar performance up to roughly 150 meters but with significantly less weight, allowing more rounds to be carried by the individual user. Complementing the P90 was the FN Five-Seven semi-automatic pistol which used the same round, promoting a higher degree of efficiency and economy through interchangeable ammunition for both primary and secondary weapons. The P90 fires at a rate of roughly 900 rounds per minute, outperforming most assault rifles by a significant margin. While the P90 never really caught on with its intended market -- that of support personnel -- it has been widely adopted by special forces groups throughout the world and is probably the most popular PDW in existence. It is highly modular, allowing for a variety of configurations using available first-party and aftermarket accessories that can be installed generally without requiring special tools or (perhaps more significantly) much time. Its standard configuration is extremely ergonomic and well-balanced, allowing it to be used effectively by just about anybody. Despite (or perhaps because of) all of this, the P90 has the unfortunate distinction of being one of the ugliest firearms ever made. Its performance, however, speaks for itself.

There are several reasons why PDWs are preferred to assault rifles in close-range engagements (specifically in the realm of urban warfare). First, if members of a special operations team are grouped tightly together, even shorter carbine-length weapons will prohibit maneuverability, never mind full-sized rifles. Second, SCHV rounds are generally over-powered for fire-fights taking place in close quarters and in the context of a battle inside a building, walls don't generally stop the bullets, increasing the likelihood of civilian casualties (which I hope everyone agrees is something to be avoided). Third, the smaller rounds produce less recoil, which increases accuracy and stability. Finally, the higher rate of fire allows engagements to end more quickly (as studies have shown that the number of shots fired in a shorter amount of time more strongly correlates to killing or disabling an opponent than does pinpoint accuracy) and reduces the chance of casualties on the assaulting group. Since most special operations occur at short ranges, this explains why PDWs wind up being the preferred weapons of choice for special forces members.

Given the success of the P90, other arms manufacturers sought to take advantage of the emerging Personal Defense Weapon market. Heckler & Koch, one of the premier arms manufacturers in Germany, created the MP7 PDW to compete with the P90. The MP7 fires a proprietary 4.6x30mm round and is smaller than H&K's best-selling MP5 SMG as well as the FN P90 while still retaining the latter's modularity. Another competitor is the Czech-made CZW-438, which fires an even smaller 4.38x30mm round. In response to Western trends toward smaller calibers, China created the QCW-05, which uses a 5.8x21mm round and is essentially a shortened version of their 5.8x41mm assault rifle ammunition. The United States military has yet to designate an official PDW and as such relies on mission-specific requirements to determine which one to use.

Criticism of the Concept

The main problems with the Personal Defense Weapon are as much theoretical as they are practical. Most obviously, the name is not an accurate reflection of their actual method of use, which has very little to do with defense. It raises the question as to whether or not a class of weapons designed around defense is appropriate for offensive use. That is to say, are armed forces simply making use of an available technology with obvious shortcomings without looking at alternatives more suited to their purposes? Next, while it's clear that PDWs have certain advantages over assault rifles in certain situations, they're not really that much better than SMGs in a lot of instances. While it is true that the 5.7x28mm round is more capable of passing through modern body armor than, say, the 9x19mm pistol round, I imagine that most people who are going to be on the receiving end of a shot from a PDW are not exactly equipped with the cutting technological edge of arms or armor. Realistically, modern PDWs are used mainly against insurgents, terrorists, guerrillas, and other likely poorly-funded individuals. Indeed, the idea has not caught on in Russia, where PDWs are basically of the Skorpion type, meaning that they use enhanced versions of established pistol calibers and are basically compact SMGs. The 9mm rounds used by Russian weapons like the PP-2000 are as effective at defeating body armor as the smaller proprietary rounds in other PDWs but are compatible with a wide range of already existing weaponry. The final major issue with the PDW is the proliferation of bizarre and completely non-standardized calibers. There is going to be almost no difference in performance between the 4.6x30mm and 4.38x30mm calibers mentioned above and no other weapons use them; what's the point? The 5.7x28mm is the only PDW round that has come close to being accepted by NATO as a standard caliber (along with 5.56x45mm and 9x19mm) but Germany balked at its acceptance over their own 4.6x30mm submission and so the process is in limbo, allowing for more of these relatively pointless calibers to come into being for no good reason. Fabrique Nationale is one of the largest and most influential arms manufacturers in the world and is almost definitely the most prestigious in Europe...and yet there are less than ten known weapons chambered for their 5.7 bullet, including the P90 and the Five-Seven. Perhaps concerned about the future of the project, FN in 2001 released the F2000, a virtual clone of the P90 chambered in 5.56x45mm.

The PDW is the perfect weapon for the fourth generation of warfare, if such a thing can be said to exist. Some have argued that the idea is phantasmal at best as it basically describes insurgencies and attempts to apply them to the broadest of historical contexts and that the basic fundamentals of state vs. state warfare haven't changed all that much since World War II. While certainly useful, the PDW concept has to move beyond its shortcomings and unite behind either a common caliber or make do with more widely used ones before it is able to stand out and make a real impact. Of all the PDWs out there, the P90 (or perhaps an improved version of it) probably has the best chance of saving the concept if only because it has already been widely dispersed around the world (particularly in NATO countries). But then again, perhaps Liechtenstein will create a new gun chambered in an experimental 4.83333x25.5mm round that will blow the competition away...

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