A former Auschwitz concentration camp prisoner,[1] he was a World War II resistance fighter as part of the Polish underground and participated in the Warsaw Uprising.

After the war he was persecuted and imprisoned by the communist Polish People's Republic due to his membership in the Home Army (Armia Krajowa, AK) and opposition activity.

[3] On 19 September 1940, Bartoszewski was detained in the Warsaw district of Żoliborz during a surprise round-up of members of the public (łapanka), along with some 2,000 civilians (among them, Witold Pilecki).

[7] From November 1942 to September 1943, Bartoszewski was an editorial team secretary of the Catholic magazine Prawda (The Truth), the press organ of the Front for the Rebirth of Poland.

[4] From fall of 1942 until spring of 1944, Bartoszewski was the editor-in-chief of the Catholic magazine Prawda Młodych (The Youth's Truth), which was also connected with the Front for the Rebirth of Poland and aimed at university and high-school students.

As a part of his activities for Żegota and the Jewish Report, he organized assistance for the participants of the Warsaw Ghetto Uprising in April 1943.

[6] On 20 September, by orders from the commandant of the Warsaw District of the AK, General Antoni "Monter" Chruściel, Bartoszewski was decorated with the Silver Cross of Merit.

[4] This was the result of a proposal put forward by the chief of the Information and Propaganda Bureau in General Headquarters of the Home Army, Colonel Jan Rzepecki).

On 1 October, he was appointed Second Lieutenant by the AK commander general Tadeusz "Bór" Komorowski (also due to a proposal by Rzepecki).

[2] He continued his underground activity in the Information and Propaganda Bureau of the Home Army at its General Headquarters in Kraków.

[2] At the end of February 1945, he returned to Warsaw, where he began his service in the information and propaganda section of NIE resistance movement.

[3] From May to August 1945, Bartoszewski was serving in the sixth unit of the Delegatura (he was responsible for information and propaganda) under the supervision of Kazimierz Moczarski).

[3] In Autumn 1945, Bartoszewski started his cooperation with the Institute of National Remembrance at the presidium of the government and the Head Commission of Examination of German Crimes in Poland.

[3] His information gathered during the occupation period about the Nazi crimes, the situation in concentration camps and prisons, as well as his knowledge concerning the Jewish genocide, appeared to be very helpful.

[3] In the articles published in Gazeta Ludowa, he mentioned the outstanding figures of the Polish Underground State (the interview with Stefan Korboński, the report from the funeral of Jan Piekałkiewicz), and the events connected with the fight for liberation of the country (a series of sketches presenting the Warsaw Uprising entitled Dzień Walczącej Stolicy).

[3] In December, he was transferred to the Mokotów Prison; he was released on 10 April 1948, with the help of Zofia Rudnicka (a former chief of Żegota, then working in the Ministry of Justice).

[8] In 1969–73, Bartoszewski served as the chairman of the Warsaw Department of the Society of Book Lovers (Towarzystwo Przyjaciół Książki) and in December 1969 he was appointed a member of the board of the Polish PEN.

In 1984, he received an honorary doctorate from Hebrew College in Baltimore (USA) as well as a certificate of the recognition from the American Jewish Committee in New York.

In the academic year 1985 he was lecturing at the Faculty of History and Social Sciences at the Catholic University of Eichstätt-Ingolstadt in the Federal Republic of Germany.

[3] Bartoszewski took part in many international conferences and seminars dedicated to the issues of World War II, the Jewish genocide, Polish-German and Polish-Jewish relationships as well as the role of Polish intellectualists in politics.

[8] In 1970, due to his opposition activity and various relations in Western countries, Bartoszewski was forbidden to publish his works in Poland (until autumn 1974).

[8] In 1974, he was engaged in activity focusing on reprieving the convicted members of the Ruch [pl] organization (among others Stefan Niesiołowski and Andrzej Czuma).

[8] After announcing martial law on 13 December 1981, he was a detainee in Białołęka prison and later in the Internment Center in Jaworze at Drawsko Pomorskie Military Training Area.

[10] On 28 April 1995, he delivered a speech during the solemn joint session of the Bundestag and Bundesrat on the occasion of the 50th anniversary of the ending of World War II as the only foreign speaker.

[10] Through his journalistic and academic activity he contributed to retaining the memory of the Polish Underground State, the Warsaw Uprising and the crimes of totalitarianism.

[10] The reason was that there was no reaction from then-Minister of Foreign Affairs Anna Fotyga to the accusations formulated by deputy Minister of Defense Antoni Macierewicz who alleged that most of hitherto Ministers of Foreign Affairs of the Third Republic of Poland were former agents of the Soviet special services according to files known as "fałszywkas" produced by the SB secret police.

[10] At a joint conference of the Polish Institute of International Affairs (PISM) and the Israel Council on Foreign Relations (ICFR) held in Warsaw in November 2017, ICFR director Laurence Weinbaum paid tribute to Bartoszewski and said he had played an important role in developing relations between Poland and Israel: "At a time when in certain quarters we are witness to shameless opportunism and the grotesque obfuscation of history, his legacy resonates especially strongly.

Bartoszewski taught people that bellicose jingoism and intolerance should not be confused with the true love of one's country and that a society that gives way to its basest instincts is doomed to ruin.