You may be familiar with the theories of military historian and conservative political adviser William S Lind, that warfare has undergone several major transformations, or generations, since the formation of nation-states.

Very briefly, First Generation, or Formation Warfare (1GW) is where armies line up in formation and fire at each other. Second Generation, or Trench Warfare (2GW) is where armies use trenches as cover from massed firepower. Third Generation, or Maneuver Warfare (3GW) is where armies exploit machinery to maneuver much more quickly than the opponent. And Fourth Generation or, Insurgent Warfare (4GW) applies asymmetrical strategy and tactics against a superior conventional military force, intending to sap the opponent nation's political will to fight.

Genghis Khan's Mongol hordes certainly won by out-maneuvering their victims, and the precepts of Sun Tzu are highly regarded, but since Lind focuses on nation-states, thousands of years of warfare between monarchies and empires don't figure into his summary. Some critics have dismissed 4GW as an inflated term for insurgency, and note that many insurgencies have been suppressed. Others note that Israeli military historian Martin van Creveld predicted much the same in his 1991 book, The Transformation of War. In 2003, Lind's theories were further discussed by retired US Marine Colonel T.X. Hammes, in The Sling and the Stone where he described 4GW as the response of practical people to a superior force.

Hammes analyzed the insurgencies that the US faced in Iraq and Afganistan and the Palestinian insurgencies in Israel, and noted that 4GW action was also how Mao took China, how the Viet Cong defeated the French, and later the Americans, how the Sandinistas took Nicaragua and how the Afghans staved off the Soviets. 4GW forces employ low-tech weaponry, Kalashnikovs and RPGs, and highly loyal cadres often under anonymous networked leadership. Their goals are economic attrition and control of political propaganda rather than quick, decisive victories. They are content to struggle for decades.

Hammes felt that 3GW armies in which the commanders don't even speak the local dialects will have little chance against embedded 4GW groups with local support. He predicted that information technology would be the key to future encounters, with dispersed, fast-evolving networks finding ways to exploit IT weaknesses. Hammes' solution was for US forces to become better trained, better-informed, more flexible and more committed—like the 4GW cadres themselves. To some extent that has happened.

The Sling and the Stone briefly discussed Fifth Generation Warfare, but in 2004 Lind warned against rushing too soon to declare a 5GW:

From what I have seen thus far, honest attempts to discover a Fifth Generation suggest that their authors have not fully grasped the vast change embodied in the Fourth Generation. The loss of the state's monopoly, not only on war but also on social organization and first loyalties, alters everything.

But there already is a 5GW Institute out there. Though they acknowledge that 5GW is as yet undefined, like Hammes they lean towards "Unrestricted Warfare":

Fifth generational warfare (5GW) theory is still being studied, not yet having a clear definition.  Some terms used have been “unrestricted warfare” or “financial jihad [warfare]”.  ... “unrestricted warfare is warfare that uses all means whatsoever - means that involve force or arms and means that do not involve force or arms; means that involve military power and means that do not involve military power; means that entail casualties and means that do not entail casualties – to force an enemy to serve one’s own interest.”

The 2001 anthrax attacks in the US, the 2004 bombings in Madrid and instances of computer hacking are often put forth as examples of 5GW. But whether we are dealing with 4GW or 5GW, it seems to me that during Insurgent Warfare the resisting forces were and are already using all means at hand, hence were and are already unrestricted. We haven't yet seen nuclear devices, but we have seen large civilian casualties in the WTC attack, Madrid bombings, Beslan School massacre, etc.

Under 4GW theory, the superior military force, which answers to its nation-state, is apparently "restricted" in that civilian massacre, such as at My Lai or Kandahar, if reported, could discredit the war or occupation effort at home. Flavius reminded us about Germans executing Belgian townsfolk, and as we are seeing in Syria right now, the 'superior forces' have certainly been known to target civilians or take any other measures available to suppress insurgencies, so it might seem naive to consider nation-states in any way restricted. But less desperate governments are at least self-restricted to what they can justify as counterinsurgency, or the acts of a lone madman, rather than war crimes.

I see these predictions of 5GW unrestricted warfare as a part of the escalation of the conflict between America and those who would rather not be part of its economic empire. Unrestricted or Jihad warfare by Al Qaeda becomes justification for less and less restricted warfare on the part of the US and its coalition. As David Coates noted, Imperial America is under increasing internal stress, and US and coalition forces have become more and more willing to conduct war in a manner that would formerly have been politically unacceptable. They have done so through controlling information and news sources, by making the war less visible, by conducting covert special ops, by conducting remote war, whether by precision bombing, attack helicopter, missiles or predator drones and through internet surveillance and exploits. And finally, they have done so under a moderate President with the tacit acquiescence of citizens who are preoccupied with domestic prosperity and are willing to overlook the faraway deaths of bystanders as collateral damage if they can keep gassing up, or charging up, their automobiles.

As Andrew Bacevich notes in Unleashed, the US increasingly relies on special forces that can be deployed without congressional approval and that can operate in secret:

Obama’s ... essential contribution has been to broaden the special ops mandate. As one observer put it, the Obama White House let Special Operations Command “off the leash.”

The displacement of conventional forces by special operations forces as the preferred U.S. military instrument—the “force of choice” according to the head of USSOCOM, Admiral William McRaven—marks the completion of a decades-long cultural repositioning of the American soldier. ... his place taken by today’s elite warrior professional.

This cultural transformation has important political implications. It represents the ultimate manifestation of the abyss now separating the military and society. ]]]

Americans have always enjoyed the political stability of both a prosperous middle class and of a citizen military that answers to the civilian government. We see that the middle class is declining. In blunt terms, in allowing an elite professional military to flourish, are we protecting ourselves, or have we sown the seeds of a future junta or military strongman?