Insurgency as a way of waging war actually dates back to classical antiquity, and thus predates the so-called second and third generations as described by Fourth Generation War theorists. Insurgents, guerillas, and resistance fighters figured large in most of the wars fought during this period. Mao was certainly not the first, nor even the most important, theorist to articulate the virtues of insurgency, or Peoples war, as it was sometimes called. Clausewitz, for one, called it a “reality of the nineteenth century,” and provided some valuable insights into its nature. Insurgency did, after all help the American colonies win independence from the British crown and it nearly thwarted the ultimate Prusso-German victory over France in the War of 1870-71. It played an important role in the histories of many Latin America states and in Western Europe and the Soviet Union during World War II as well as enabling the emergence of Israel in the late 1940s.
Portraying changes in warfare in terms of “generations” implies that each one evolved directly from its predecessor, and, as per the natural progression of generations, eventually displaced it. So, gentlemen, you often get the answer if you look back in history. Fact is that the concept of insurgency is well known and we fight it quite effectively.