Afer the war, Fieldorf remained on active duty, was promoted to the rank of major and as such he was posted to the Polish Legion’s First Infantry Regiment as a battalion commander. In 1931, he became its second-in-command. In 1932, he became a lieutenant colonel. Three years later, Fieldorf was transferred to the position of a commander of the “Troki” independent battalion of the Border Guard Corps (KOP) in the KOP’s “Wilno” Regiment. In 1936, he was made the district commander of the Polish Riﬂemen’s Association in France.
In March 1938, Fieldorf became the commander of the 51st Giuseppe Garibaldi Riﬂemen’s Regiment in Brzeżany in the eastern fringes of Poland. He was with the regiment for the whole military campaign during the Polish Defensive War of 1939. Afer the battle of Iłża, he reached his native Kraków. He was stopped at the Slovak border during an attempt to get to the West to join the Polish Army under formation. He was interned, but managed to escape from a camp and reached France, where he later completed staﬀ courses and was promoted to full colonel on 3 May 1940. Afer the capitulation of France and after the Polish authorities and the army moved to the United Kingdom, he was appointed the first emissary of the Government-in-Exile and Commander-in-Chief to Poland. On 17 July 1940, Fieldorf set out from London to Warsaw, which he reached on 6 September.
Fieldorf was active in the Union of Armed Struggle in Warsaw and later, from 1941, in Vilnius and Białystok. In 1942, he was appointed a commander of Kedyw (directorate of underground sabotage operations) of the High Command of the Home Army. It was on his order that the German SS General Franz Kutschera was assassinated in Warsaw.
In April 1944, Fieldorf started to form a highly secretive Niepodległość (NIE) organisation, which was designed to continue operations during the expected Soviet occupation of Poland. On the order of the Supreme Commander Kazimierz Sosnkowski of 28 September 1944, he was promoted to the rank of brigadier general. In October 1944, he became the Deputy Commander-in-Chief of the Home Army under General Leopold Okulicki and kept the post till 19 January 1945 when the Home Army was disbanded.
On 7 March 1945, Fieldorf was arrested by the Soviet NKVD in the town of Milanówek under the false name of Walenty Gdanicki. Unrecognized as a general, ‘Nil’ was transferred from the NKVD headquarters in Włochy to a camp in Rembertów, and on 21 March 1945 he was sent to the labour camps of Bieriozovka, Stupino and Hudiakowo, in the Ural Mountains . After serving his sentence, he was released and returned to Poland in October 1947. Under his assumed name, he settled in Biała Podlaska, abandoning his underground activities. After moving between Warsaw and Kraków, he fnally settled in Łódź.
On 10 November 1950, he was arrested by the Regional Military Replenishment Unit in Łódź, transferred to Warsaw and placed under arrest in Rakowiecka Street. On 16 April 1952, he was sentenced to death as a ”fascist-Hitlerite criminal”. The sentence was carried out, by hanging, on 24 February 1953. In July 1958, the Prosecutor’s Office discontinued the investigation against General August Emil Fieldorf, citing lack of evidence of guilt. In March 1989, he was rehabilitated afer it was found that “he had not committed the crime he was accused of”. The remains of the hero have not been found until today
by Tadeusz Płużański