The war of 1920: how Polish codebreakers read the Red Army’s messages

A war in which radio spoke

Marek Grajek, who has studied the files of Polish radio intelligence, notes that Polish units were ordered to damage wire networks, which forced Soviet units to use radio – and radio could be listened to.³

In its resolution of 17 October 2019 establishing 2020 as the Year of Jan Kowalewski, the Senate of Poland states that Polish scientists then created the most modern radio-electronic intelligence service in Europe, and that the plan for the Battle of Warsaw was based on information gathered by Polish radio intelligence.¹

According to the monograph published with the ABW, listening was carried out by 6 fixed and 26 field radio stations, deployed from Poznań, Grudziądz and Kraków up to the front line. One of the men at the headphones was Maksymilian Ciężki, who in 1919–1920, as commander of the radio station in Wilno (Vilnius), decrypted Soviet radiograms and later worked at the Cipher Bureau.^2,4

A lieutenant from Łódź

Jan Kowalewski was born in Łódź in 1892. According to the Senate resolution, he began breaking Bolshevik ciphers in the autumn of 1919.¹

Grajek relates the story of how it began: in the summer of 1919 Kowalewski covered a night shift for a colleague who wished to dance at his sister’s wedding. He had no experience with ciphers but knew Russian well, and by morning he had broken the first Soviet message. He was then moved to the cipher section of the General Staff.³

In 1919–1921 he headed Section 2 (Foreign Ciphers) of the Cipher Bureau of the Second Department of the Polish Army High Command, which served as the radio intelligence centre. He himself recalled that he had been decorated for the results achieved in 1919 and 1920.²

Mathematicians in uniform

Three professors of the University of Warsaw volunteered for Kowalewski’s team: Stanisław Leśniewski, Stefan Mazurkiewicz and Wacław Sierpiński. Mazurkiewicz worked directly with Kowalewski; Grajek credits Sierpiński with breaking a new key in early August 1920.^2,3

Grzegorz Łukomski regards the experience of radio intelligence in the 1920 war, especially its final phase, as one of the sources of later successes. In 1931 the Radio Intelligence Section and the Own Ciphers Section of the Second Department were merged to form the Cipher Bureau, which again turned to mathematicians. The story of Marian Rejewski and his colleagues is told on the card Breaking Enigma.⁴

Why the messages could be read

Grajek, who has examined the surviving files, describes the Soviet systems: most military messages took the form of five-digit groups, and the basic keys were simple monoalphabetic substitutions based on an extended 10 × 10 Polybius square. Some keys were complicated with extra symbols, transposition or superencipherment (see cipher and cryptanalysis).³

The weakness lay in practice. According to Grajek, new tables were made by shifting old ones, the same superencipherment keys were reused, key references were sent in clear, and military jargon supplied reliable cribs. He considers the loss of the “Delegate” key the biggest blunder: Kowalewski broke it cryptanalytically, and Polish intelligence also seized a copy.³

August 1920

The best-known episode concerns the “Revolution” cipher. The ABW monograph states that it was introduced at the end of the first ten days of August 1920, on the eve of the assault on Warsaw, and was broken within a few hours by Kowalewski and Professor Stefan Mazurkiewicz. It carried the 16th Army’s order of 12 August to storm Warsaw; Kowalewski recalled that he passed it by telephone to the Belweder, to Józef Piłsudski, still in the original, before translation.²

According to the Senate resolution, orders to specific Soviet divisions were on Piłsudski’s desk the day after they were sent. In a document of 19 August 1920, based on intercepted radiograms, Kowalewski reported that Budyonny was still near Lwów (Lviv), despite Tukhachevsky’s directive sending his cavalry army towards Włodzimierz Wołyński (Volodymyr).^1,2

Grajek adds two earlier examples: the codebreakers warned of the transfer of Budyonny’s First Cavalry Army from the Caucasus to the Polish front, which changed the situation in Ukraine, and after Denikin’s defeat they detected a Soviet build-up that the author regards as evidence of Moscow’s aggressive intentions.³

Exactly how many messages were read is not known. The monograph cites Mieczysław Wyżeł-Ścieżyński, author of Radiotelegrafia jako źródło wiadomości o nieprzyjacielu (Radiotelegraphy as a source of information about the enemy, Przemyśl 1928), for a figure of 410 Soviet messages read in August 1920 alone, noting that he did not know the full number.²

According to media and secondary accounts · not confirmed by official sourcesThe Polish Press Agency, citing historians’ work, reports that nearly 400 Soviet messages were decrypted between August 1919 and February 1920, and that 41 ciphers were broken between June and October 1920, 22 of them by Kowalewski.⁵

An archive that survived

The files of Polish radio intelligence had a turbulent history. According to Grajek, in 1939 the Germans seized part of the holdings of the Central Military Archives and took them to Oliva near Danzig, where the Abwehr examined them. Around 1945 the Soviets moved them to the Soviet State Archive and later, at an unknown date, returned them to Poland. They ended up in the archive of the communist secret police; after the regime fell they were found during a review of the holdings and returned to the Central Military Archives. The digitised collection runs to more than 20,000 pages, including key books for Soviet ciphers and for those of Denikin’s and Wrangel’s armies.³

Grajek also explains why the story long remained little known: codebreaking files were closely guarded, in 1939 the Cipher Bureau destroyed or evacuated most traces of its work, and in communist Poland the archive was inaccessible, partly because it recorded a Polish victory over what was then an ally.³

In 2017 the Polish radio intelligence documents from the period of the Battle of Warsaw in 1920, held in the Central Military Archives, were inscribed on UNESCO’s Memory of the World Register. Kowalewski died in exile in London in 1965; the Senate honoured him with a resolution in 2019.^1,6

Kowalewski’s later life goes beyond the 1920 war: according to the ABW monograph, in Japan he trained Japanese officers in the use of ciphers.²

According to media and secondary accounts · not confirmed by official sourcesThe Polish Press Agency reports that he ran the course in Tokyo in 1923, that from 1941 he headed the Lisbon post of Akcja Kontynentalna (Continental Action), and that he received the Virtuti Militari Cross, 5th class, for his part in defeating the Soviets. On 22 September 2020 President Andrzej Duda posthumously promoted him to brigadier general.⁵

A reviewer from the Military Historical Bureau highlights Grzegorz Nowik’s study, which links Piłsudski’s plan to defeat the Soviet armies one after another with the data supplied by radio intelligence under Kowalewski, and Andrzej Kowalski’s argument that Soviet intelligence failed because of the removal of experts from the former tsarist army, the amateurism of party activists and the terror of the Cheka (see Cheka).⁷