During World War II, he served in occupied Poland as officer of the underground resistance organizations, including Związek Walki Zbrojnej, and Armia Krajowa.

[1] In the interwar Poland Klukowski was the editor-in-chief of two magazines, Teka Zamojska and Kwartalnik Regionalny in Zamość.

Following World War II, he wrote two nominal works about his experiences, the Journal from the Years of Occupation of Zamojszczyzna, 1939–44 (Polish: Dziennik z lat okupacji Zamojszczyzny 1939–1944),[2] a detailed account of his experiences as medical doctor in the General Government territory of occupied Poland during World War II, as well as the Red Shadow: A Physician's Memoir of the Soviet Occupation of Eastern Poland, 1944–1956.

Only recently Klukowski has gained international recognition as an important primary witness and chronicler of the World War Two period in Polish historiography.

His descriptions of life under the Nazis are cited extensively by Richard J. Evans in The Third Reich at War, among other historians.