S . L . A . Marshall S . L . A . Marshall ( full name , Samuel Lyman Atwood Marshall ) ( July 18 , 1900 – December 17 , 1977 ) was a chief U . S . Army combat historian during World War II and the Korean War . He authored some 30 books about warfare , including " Pork Chop Hill : The American Fighting Man in Action , " which was made into a film of the same name . Early life . Marshall was born in Catskill , New York and first served in the Army as an enlisted man in World War I with the U . S . 90th Infantry Division . While his writings stated that he was an officer who led troops in combat , Marshall did not fight and was commissioned an officer in April 1919 to assist in demobilization . After that he worked as a newspaper reporter . World War II combat historian . During World War II Marshall became an official Army combat historian , and came to know many of the war ' s most well known Allied commanders , including George S . Patton and Omar N . Bradley . He conducted hundreds of interviews of both enlisted men and officers regarding their combat experiences , and was an early proponent of oral history techniques . In particular , Marshall favored the group interview , where he would gather surviving members of a frontline unit together and debrief them on their combat experiences of a day or two before . Marshall ' s work on infantry combat effectiveness in World War II , titled " Men Against Fire " , is his best - known and most controversial work . In the book , Marshall claimed that of the World War II U . S . troops in actual combat , 75 % never fired their personal weapons at the enemy for the purpose of killing , even though they were engaged in combat and under direct threat . Marshall argued that the United States Army should devote significant training resources to increase the percentage of soldiers willing to engage the enemy with direct fire . Less well known , but perhaps more significant was Marshall ' s effort to assemble German officers after the war to write histories and analyses of battles in all theatres of the European war . At the height of the project over 200 German officers participated , including Heinz Guderian and Franz Halder . Hundreds of monographs came out of the project , of which three are available in commercial print ( see " Anvil of War : German Generalship in Defense of the Eastern Front " , edited by Peter G . Tsouras , 1994 . ) Korean War . Marshall was recalled from the Reserves in late 1950 for three months ' duty as a Historian / Operations Analyst for the Eighth Army during the Korean War . He collected his numerous Korean combat interviews into a treatise analyzing U . S . infantry and weapons effectiveness , " Commentary on Infantry and Weapons in Korea 1950 – 51 " . The U . S . Army decided to classify some of Marshall ' s findings as restricted information , later incorporating them as part of a plan to improve combat training , weapons , equipment , and tactics . Retirement , Vietnam tour and death . Following his retirement from the Army Reserve in 1960 , with the rank of brigadier general , Marshall continued to serve as an unofficial adviser to the Army . As a private citizen , he spent late 1966 and early 1967 in Vietnam on an Army - sponsored tour for the official purpose of teaching his after - action interview techniques to field commanders , in order to improve data collection for both the chain of command and the future official history of the Vietnam War . The Army Chief of Military History ' s representative on the tour , Colonel David H . Hackworth , collected his own observations from the trip and published them as " The Vietnam Primer , " giving Marshall credit as co - author . Marshall died in 1977 in El Paso , Texas . The University of Texas at El Paso library has a special collection built around his books . Marshall is used as a character in " " , a video game released in 2005 . Controversy after death . Certain professional soldiers have publicly cast doubt on Marshall ' s research methodology . Professor Roger J . Spiller ( Deputy Director of the Combat Studies Institute , US Army Command and General Staff College ) demonstrated in his 1988 article " S . L . A . Marshall and the Ratio of Fire " ( " RUSI Journal " , Winter 1988 , pages 63 – 71 ) that Marshall had not actually conducted the research upon which he based his ratio of fire theory . " The ' systematic collection of data ' appears to have been an invention . " This revelation called into question the authenticity of some of Marshall ' s other books , and lent academic weight to doubts about his integrity that had been raised in military circles even decades earlier . The controversial figure Col . David Hackworth , writing in his 1989 memoir " About Face " , described at length his initial elation at an assignment with a man he idolized , and how that elation turned to bitter disillusionment after seeing Marshall ' s character and methods firsthand . Hackworth described Marshall as a " voyeur warrior " for whom " the truth never got in the way of a good story , " and went so far as to say " Veterans of many of the actions he ' documented ' in his books have complained bitterly over the years of his inaccuracy or blatant bias " . Marshall ' s grandson , journalist John Douglas Marshall , has explored his grandfather ' s posthumous reputation in a series of articles in the " Seattle Post - Intelligencer " and later in a book , " Reconciliation Road : A Family Odyssey of War and Honor . " After a review of the general ' s archives and other memorabilia , as well as interviews with many of his contemporaries and associates , the younger Marshall concludes that the body of his grandfather ' s work still has value .