Three Generations of Warfare 
While military development is generally a continuous evolutionary process, the modern era has witnessed three watersheds in which change has been dialectically qualitative. Consequently, modern military development comprises three distinct generations. 
First generation warfare reflects tactics of the era of the smoothbore musket, the tactics of line and column.  These tactics were developed partially in response to technological factors — the line maximized firepower, rigid drill was necessary to generate a high rate of fire, etc.— and partially in response to social conditions and ideas, e.g., the columns of the French revolutionary armies reflected both the élan of the revolution and the low training levels of conscripted troops. Although rendered obsolete with the replacement of the smoothbore by the rifled musket, vestiges of first generation tactics survive today, especially in a frequently encountered desire for linearity on the battlefield.[... ]
Second generation warfare was a response to the rifled musket, breechloaders, barbed wire, the  machinegun, and indirect fire. Tactics were based on fire and movement, and they remained essentially  linear. The defense still attempted to prevent all penetrations, and in the attack a laterally dispersed line advanced by rushes in small groups. Perhaps the principal change from first generation tactics was heavy reliance on indirect fire; second generation tactics were summed up in the French maxim, "the artillery conquers, the infantry occupies." Massed firepower replaced massed manpower.[...]
While ideas played a role in the development of second generation tactics (particularly the idea of lateral dispersion), technology was the principal driver of change.[...]
Third generation warfare was also a response to the increase in battlefield firepower. However, the driving force was primarily ideas. Aware they could not prevail in a contest of materiel because of their weaker  industrial base in World War I, the Germans developed radically new tactics. Based on maneuver rather than attrition, third generation tactics were the first truly nonlinear tactics. The attack relied on infiltration to bypass and collapse the enemy's combat forces rather than seeking to close with and destroy them. The defense was in depth and often invited penetration, which set the enemy up for a counterattack. 
While the basic concepts of third generation tactics were in place by the end of 1918, the addition of a new  technological element-tanks-brought about a major shift at the operational level in World War II. That shift was blitzkrieg.[...]
Thus we see two major catalysts for change in previous generational shifts: technology and ideas. What perspective do we gain from these earlier shifts as we look toward a potential fourth generation of warfare? 

Elements That Carry Over 
Earlier generational shifts, especially the shift from the second to the third generation, were marked by growing emphasis on several central ideas. Four of these seem likely to carry over into the fourth generation, and indeed to expand their influence. 
The first is mission orders. Each generational change has been marked by greater dispersion on the battlefield. The fourth generation battlefield is likely to include the whole of the enemy's society.[...]
Second is decreasing dependence on centralized logistics. Dispersion, coupled with increased value placed on tempo, will require a high degree of ability to live off the land and the enemy.
Third is more emphasis on maneuver. Mass, of men or fire power, will no longer be an overwhelming factor. In fact, mass may become a disadvantage as it will be easy to target. Small, highly maneuverable, agile forces will tend to dominate.
Fourth is a goal of collapsing the enemy internally rather than physically destroying him. Targets will include such things as the population's support for the war and the enemy's culture. Correct identification of enemy strategic centers of gravity will be highly important.

In broad terms, fourth generation warfare seems likely to be widely dispersed and largely undefined; the distinction between war and peace will be blurred to the vanishing point. It will be nonlinear, possibly to the point of having no definable battlefields or fronts. The distinction between "civilian" and "military" may
disappear. Actions will occur concurrently throughout all participants' depth, including their society as a cultural, not just a physical, entity. Major military facilities, such as airfields, fixed communications sites, and large headquarters will become rarities because of their vulnerability; the same may be true of civilian equivalents, such as seats of government, power plants, and industrial sites (including knowledge as well as manufacturing industries). Success will depend heavily on effectiveness in joint operations as lines between responsibility and mission become very blurred. Again, all these elements are present in third generation warfare; fourth generation will merely accentuate them. 

Potential Technology-Driven Fourth Generation 
If we combine the above general characteristics of fourth generation warfare with new technology, we see one possible outline of the new generation. For example, directed energy may permit small elements to destroy targets they could not attack with conventional energy weapons. Directed energy may permit the achievement of EMP (electromagnetic pulse) effects without a nuclear blast.[...]
Leaders will have to be masters of both the art of war and technology, a difficult combination as two different mindsets are involved. Primary challenges facing commanders at all levels will include target selection (which will be a political and cultural, not just a military, decision), the ability to concentrate suddenly from very wide dispersion, and selection of subordinates who can manage the challenge of minimal or no supervision in a rapidly changing environment.[...]
Psychological operations may become the dominant operational and strategic weapon in the form of
media/information intervention. Logic bombs and computer viruses, including latent viruses, may be used to disrupt civilian as well as military operations. Fourth generation adversaries will be adept at manipulating the media to alter domestic and world opinion to the point where skillful use of psychological operations will sometimes preclude the commitment of combat forces. A major target will be the enemy population's support of its government and the war. Television news may become a more powerful operational weapon than armored divisions. [...]
A major caveat must be placed on the possibility of a technologically driven fourth generation, at least in the American context. Even if the technological state of the art permits a high-technology fourth generation and this is not clearly the case — the technology itself must be translated into weapons that are effective in actual combat. At present, our research, development, and procurement process has great difficulty making this transition. It often produces weapons that incorporate high technology irrelevant in combat or too complex to work in the chaos of combat. Too many so-called "smart" weapons provide examples; in combat they are easy to counter, fail of their own complexity, or make impossible demands on their operators. The current American research, development, and procurement process may simply not be able to make the transition to a militarily effective fourth generation of weapons.

A Potential Idea-Driven Fourth Generation
Technology was the primary driver of the second generation of warfare; ideas were the primary driver of the third. An idea-based fourth generation is also conceivable. For about the last 500 years, the West has defined warfare. For a military to be effective it generally had to follow Western models. Because the West's strength is technology, it may tend to conceive of a fourth generation in technological terms.
However, the West no longer dominates the world. A fourth generation may emerge from non-Western cultural traditions, such as Islamic or Asiatic traditions. The fact that some non-Western areas, such as the Islamic world, are not strong in technology may lead them to develop a fourth generation through ideas rather than technology.
The genesis of an idea-based fourth generation may be visible in terrorism. This is not to say that terrorism is fourth generation warfare, but rather that elements of it may be signs pointing toward a fourth generation. Some elements in terrorism appear to reflect the previously noted "carryovers" from third generation war fare. The more successful terrorists appear to operate on broad mission orders that carry down to the level of the individual terrorist. The 'battlefield" is highly dispersed and includes the whole of the enemy's society. The terrorist lives almost completely off the land and the enemy. Terrorism is very much a matter of maneuver: the terrorist's firepower is small, and where and when he applies it is critical.
Two additional carryovers must be noted as they may be useful "signposts" pointing toward the fourth generation. The first is a component of collapsing the enemy. It is a shift in focus from the enemy's front to his rear.[...] Terrorism takes this a major step further. It attempts to bypass the enemy's military entirely and strike directly at his homeland at civilian targets. Ideally, the enemy's military is simply irrelevant to the terrorist.
The second signpost is the way terrorism seeks to use the enemy's strength against him.[...]
Terrorists use a free society's freedom and openness, its greatest strengths, against it. They can move freely within our society while actively working to subvert it. They use our democratic rights not only to penetrate but also to defend themselves.[...] If we are forced to set aside our own system of legal protections to deal with terrorists, the terrorists win another sort of victory. [...]
The contradiction between the military culture and the nature of modern war confronts a traditional military Service with a dilemma. Terrorists resolve the dilemma by eliminating the culture of order. Terrorists do not have uniforms, drill, saluting or, for the most part, ranks. Potentially, they have or could develop a military culture that is consistent with the disorderly nature of modern war. The fact that their broader culture may be non-Western may facilitate this development.
Even in equipment, terrorism may point toward signs of a change in generations. Typically, an older
generation requires much greater resources to achieve a given end than does its successor. Today, the
United States is spending $500 million apiece for stealth bombers. A terrorist stealth bomber is a car with a bomb in the trunk—a car that looks like every other car.

Terrorism, Technology, and Beyond
Again, we are not suggesting terrorism is the fourth generation. It is not a new phenomenon, and so far it has proven largely ineffective. However, what do we see if we combine terrorism with some of the new technology we have discussed? For example, that effectiveness might the terrorist have if his car bomb were a product of genetic engineering rather than high explosives? To draw our potential fourth generation out still further, what if we combined terrorism, high technology, and the following additional elements?
 A non-national or transnational base, such as an ideology or religion. Our national security capabilities are designed to operate within a nation-state framework. Outside that framework, they have great difficulties. The drug war provides an example.[...]
 A direct attack on the enemy's culture. Such an attack works from within as well as from without. It can bypass not only the enemy's military but the state itself. The United States is already suffering heavily from such a cultural attack in the form of the drug traffic. Drugs directly attack our culture. They have the support of a powerful "fifth column," the drug buyers. They bypass the entire state apparatus despite our best efforts. Some ideological elements in South America see drugs as a weapon; they call them the "poor man's intercontinental ballistic missile.".[...] 
Highly sophisticated psychological warfare, especially through manipulation of the media, particularly television news. Some terrorists already know how to play this game. More broadly, hostile forces could easily take advantage of a significant product of television reporting — the fact that on television the enemy's casualties can be almost as devastating on the home front as are friendly casualties.[...]
All of these elements already exist... Would such a combination constitute at least the beginnings of a fourth generation of warfare? One thought that suggests they might is that third (not to speak of second) generation militaries would seem to have little capability against such a synthesis. This is typical of generational shifts.

The purpose of this paper is to pose a question, not to answer it. The partial answers suggested here may in fact prove to be false leads. But in view of the fact that third generation warfare is now over 70 years old, we should be asking ourselves the question, what will the fourth generation be?