From the Philippine Insurrection to the War in Afghanistan, America's warriors have experienced what Robert Taber calls, "the war of the flea." The flea is the guerrilla, and the dog is the government or occupying power. Experience has taught us that irregular warfare (IW) is more difficult than operations against an enemy that fights according to the conventional paradigm. The authors have participated in all six IW activities, which include: Foreign internal defense (FID), counterterrorism (CT), counterinsurgency (COIN), security force assistance (SFA), stability operations (SO), and, in a more limited sense, unconventional warfare (UW). Our experience is primarily at the tactical level. We took part in combat operations in Iraq, Afghanistan, and the Philippines, peacetime stability operations (SO) in places like Bosnia, and foreign internal defense (FID) missions on five continents. Across the spectrum, in every theater, we witnessed dogged American stamina, professionalism, and ingenuity in the tackling of a myriad of difficult missions. What we discovered from our experiences is this: echoing the sentiment of General Cleveland, in each conflict "American tactical brilliance was followed by strategic muddling and eventual failure." This book investigates the American way of irregular warfare, and it will be argued that America has a distinct formula for success; one that has been largely forgotten. It is our humble opinion, the U.S. Military fails to adequately hand down hard-earned lessons-learned in its institutional memory. It is hoped that this book will serve as a prescription. With that being said, we hold no expectation that our analysis constitutes the silver bullet remedy to irregular warfare success. Nonetheless, it is hoped that this book will arm America's irregular warfare practitioners with conceptual tools that will enable them to win the war of the flea and bring glory and honor to our standard.