Czerniawski graduated in the late 1930s from the Wyższa Szkoła Wojenna, a military academy at Warsaw in Poland. As a former officer of the Polish Air Force, he volunteered to create an allied espionage network in France in 1940. He set it up with Mathilde Carré who recruited the agents; some French declined to work for a Pole. This network was code-named Interallie. Czerniawski was evacuated to Britain to be examined by Polish intelligence and then meet General Sikorski where he was presented with the Virtuti Militari. He was returned to France by parachute in November 1941. On 17 November 1941 the Abwehr group of Hugo Bleicher arrested Czerniawski and then Carré. The network had been uncovered due to the lack of proper operational security within the organisation, and many other members of the Interallie were picked up after Carré agreed to co-operate with the Germans in return for her life. Czerniawski and others were imprisoned. After having been offered safety by the Germans, he was sent to England as an agent. However, he made himself known to the British authorities. He was de-briefed by the British and Polish authorities about the security lapses of his organisation in France. He was then employed as a double agent by MI5 using the codename "Brutus" under their Double Cross System. His strong anti-Russian attitude, manifested in his denouncing a Polish officer who attended an official reception at the Soviet Embassy, led to doubts about his suitability. For this act of mutiny against the Polish authorities, he was arrested and imprisoned. MI5 produced a cover story that he had been detained in a sweep of "anti-Bolshevik" Poles. A Polish court martial found him guilty of gross insubordination, but to keep the matter quiet sentenced him to only two months imprisonment. After his release from prison, Czerniawski was unrepentant to his handlers; MI5 doubted his reliability, thinking him fickle and liable to meddle, and MI5 also harboured concerns that the Germans would be suspicious about his arrest and swift release. He was no longer permitted to operate the radio himself and he was only used for distribution of low grade information. Initial German suspicion faded and in December 1943 the British decided to use Brutus for distribution of important deception information. Therefore, he played a major part in the allied deception prior to the D-Day landings in Normandy in 1944 as one of the primary agents passing false information as part of Fortitude South, the deception plan aimed at convincing Germany that the Allies would invade Europe in the Pas de Calais area across the English Channel from South-East England. After the war he stayed in the UK and wrote The Big Network, published in 1961. Czerniawski died in London, on 26 April 1985, at the age of 75. He was buried in Newark-on-Trent in Newark Cemetery for RAF burials.
