Chrobry II Battalion The Chrobry II Battalion was a unit , formally subordinate to the Polish Home Army ( AK ) , which took part in the Warsaw Uprising . It was named after the Polish king Bolesław I Chrobry ( " Chrobry " is old Polish for " valiant " ) . Formation and name . It was formed as a battalion on August 1 , 1944 , on the day of the break out of the Warsaw Uprising . Later it was expanded to a Battalion group . Its first commander was Major Leon Nowakowski ( " Lig " ) . Later the Battalion group was led by Major Zygmunt Brejnak . However , the organization of the unit was carried out without direct oversight of the Home Army High Command and soon it turned out that there was another battalion of the same name operating in the same area of Warsaw , under the command of Major Gustaw Billewicz ( " Sosna " - Pine ) . As a result the unit was designated with the Roman numeral " II " and subordinated to the commander of the 1st Region Śródmieście ( City center ) Edward Pfeiffer . Because of the independent nature in which the unit was formed it contained soldiers of various underground formations and ideological backgrounds , including those from the Home Army , from the right - wing National Armed Forces ( NSZ ) as well as from the communist Armia Ludowa ( AL ) . The battalion fought in the city center and on the 3rd of August its companies , led by Lieutenant Zbigniew Brym carried out a successful assault on the Post Office Rail Station , located at the crossing of the Żelazna St . and Aleje Jerozolimskie . On the 8th of August it captured the building of the Ministry of Waterworks and Sewage on Starynkiewicz St . , which it lost four days later having to retreat in after an attack by the Russian - collaborationist Kaminski Brigade . Discovering the Prosta Street murders . During the uprising , a captain in the battalion , Wacław Zagórski ( " Leszek " ) discovered that some insurgents ( a group of 8 to 10 men ) from a different unit , under command of an officer named Stykowski ( " Hal " ) , had murdered some Jews who had emerged from hiding . Together with Roman Bornstein , Chrobry battalion ' s medic ( who was Jewish ) , he reported the crime to the AK High Command and later published an account of it . According to Bornstein , they met with the commander of the uprising , Antoni Chruściel ( " Monter " ) who was outraged at the crime , ordered an immediate investigation and court martial of those responsible . The resulting investigation by the Home Army ' s security services led to the arrest of one person , Robert Kaminski , ( " Francuz " ) and an arrest warrant for another , Cpl . Mucha , with the recommendation that they both be executed under martial law . Kaminski ' s eventual fate however is unknown and Mucha died , killed in the fighting before he could be arrested . Some sources have questioned whether Kaminski was in fact responsible for the murders or whether he served as a patsy for Stykowski . Further investigations were suspended when it was discovered that the remaining perpetrators had either been killed in fighting or by members of their own unit . In particular , Stykowski ' s own men shot a Corporal Unrug whom they blamed for the murders , supposedly because they had been disgusted by his actions . However , it is also possible that Unrug was killed in order to keep him from implicating Stykowski ( who was never prosecuted ) in the crime . The investigation also revealed that Stykowski ' s men had also killed members of the Chrobry II unit out of robbery motives . After the war , in some accounts , the Chrobry II unit has been mistakenly blamed for the murders , because they controlled an area neighboring the one in which the murders were committed , whereas in fact , it was actually one of the senior officers of the unit who exposed the crime . Notable soldiers of the unit . At its height , the battalion group Chrobry II had 3200 personnel , including 3000 soldiers . During the uprising , about 400 of them were killed . One of the platoons of the battalion was led by the author of the first ever report about the Holocaust , Witold Pilecki , later executed by the Polish communist secret police . Notable soldiers of battalion , in addition to those mentioned above , included Tadeusz Siemiątkowski and Mirosław Biernacki The unit has also been noted for having a high number of Jewish soldiers in its ranks , most of whom emerged from hiding upon the break out of the uprising . These included the diarist Calel Perechodnik , who actually served with a nationalist right wing NSZ platoon , and Jakub Michlewicz , who at 15 years old was the youngest member of the battalion .