Ciechanów Military District. In August 1919, in connection with the outbreak of the First Silesian Uprising, he became the head of the branch of the Supreme Command for the Silesian Uprising with the task of managing the insurgent action in Upper Silesia. During the Polish-Soviet War, he took over a section of the front near the Berezina River. He served as the commander of the 2nd Brigade and then the 2nd Legions Infantry Division. For his performance during this phase of the war, he was awarded the Virtuti Militari V class. Post war After the war, he was sent to Paris, where he graduated from École spéciale militaire de Saint-Cyr. He then completed an internship at the French General Staff. Upon his return, he was promoted to General. Żymierski served in Warsaw as the Deputy Chief of Administration of the Polish Army. Żymierski was appointed deputy head of the Army Administration for Armaments, where he was responsible for finances and purchases of military equipment at the Ministry of Military Affairs. One of his subordinates and later Prime Minister Felicjan Sławoj Składkowski, in his memoirs written in exile succinctly commented on his economic talents. In his 1921 opinion about Żymierski, Marshal Edward Rydz-Śmigły wrote: "A very good officer of the General Staff in the higher commands, talented, very dutiful, very active, excellent educator of the officer corps, very good administrator, with great initiative." During the 1926 coup d'état, he defended the democratically elected government of Stanisław Wojciechowski. After the coup, in 1927, the new sanacja regime of Marshal Józef Piłsudski charged him with bribery and embezzlement. Following an official investigation, he was court-martialled and demoted to private first class, expelled from the army and sentenced to five years in prison. Karol Popiel later claimed that accusing Żymierski of corruption was a kind of political revenge on the part of Józef Piłsudski and was supposed to indirectly discredit Władysław Sikorski. Upon his release in 1931, Żymierski went to France. He was recruited by Soviet intelligence and became a well-paid secret agent delivering information about the Franco-Polish alliance. He joined the Communist Party of Poland. His secret engagement with Moscow was discontinued when Stalin ordered the dissolution of the Polish Communist Party (KPP) in 1938 during the Great Purge. World War II Żymierski returned to Poland shortly before the Nazi-Soviet invasion of Poland at the onset of World War II, and soon resumed