LESSONS IN THE ESSENTIAL ELEMENTS OF GUERRILLA WARFARE ARE PROVIDED BY CASES STUDIES OF MAJOR INSURGENCIES SINCE WORLD WAR II. THE LAWS AND PRINCIPLES OF GUERRILLA WARFARE INCLUDE MOBILITY, CAPACITY FOR SURPRISE, IN DEPTH WAR, THE NEED FOR DISCIPLINE AND MORALE, THE MORALE APPEAL, AND THE NEED FOR POPULAR SUPPORT. DISCUSSION OF THE CAUSES THAT LEAD TO GUERRILLA WARFARE EXAMINES THE BAY OF PIGS AND THE WAR IN THE PHILLIPPINES WITH THE HUKS. THE DIFFERENCES BETWEEN GENUINE AND SYNTHETIC CAUSES AND THE EFFECTS OF THIS DIFFERENCE ON AN INSURGENCY ARE CONSIDERED. DISCUSSION OF OTHER ELEMENTS OF WARFARE USES PARTICULAR EXAMPLES: (1) LEADERSHIP EXPLORES THE EXAMPLE OF TITO AND THE PARTISAN MOVEMENT IN YUGOSLAVIA SHOWING THAT A FEW WELL TRAINED LEADERS CAN RUN A LIBERATION MOVEMENT. (2) THE DEVELOPMENT OF A WAR IS EXEMPLIFIED BY GENERAL GIAP IN NORTH VIETNAM'S FIGHT AGAINST THE FRENCH. (3) THE NEED FOR A BASE IS SHOWN IN THE INSURGENCY BETWEEN GREECE AND YUGOSLAVIA; (4) THE NEED TO ISOLATE THE ENEMY FROM POTENTIAL AID IS SEEN IN THE WAR IN MALAYA; AND (5) THE USE OF TERROR AND REPRISALS, AND THE POSSIBILITIES OF TERROR AS A FORCE OF INTERNAL DISCIPLINE ARE SEEN THROUGH THE CAMPAIGN IN CYRUS. GUERRILLA WARFARE AS AN AUXILLARY TO CONVENTIONAL WARFARE IS EXAMINED, AS IS THE POSSIBILITY OF URBAN GUERRILLA WARFARE IN LATIN AMERICA. THROUGHOUT THE BOOK, CONSTANT REFERENCE IS MADE TO THE GREAT GUERRILLA THEORISTS, SUCH AS MAO, AND BOTH THEORY AND PRACTICE ARE ANALYZED CONCERNING A PARTICULAR GUERILLA 8CTION. IN THE DISCUSSION OF TERROR, AN EVALUATION IS MADE OF THE LIKELIHOOD OF BRITISH AND AMERICAN FORCES BEING ABLE TO USE IT, AND THE VARYING LEVELS OF TOLERANCE FOR TERROR FOUND IN VARIOUS COMMUNITIES THROUGHOUT THE WORLD. AN INDEX IS INCLUDED. (RFC)