While Germany boiled in the fires of revolution, paralysed by Ludendorff and Hindenburg's Kapp Putsch, Vladimir Lenin ordered the recovery of the territories lost to Poland, as well as West Ukraine. The Kingdom of Yurizlansia had been mauled by Nestor Makhno's Black Army, which at the time was allied with the Bolsheviks, and only held control of the country's western parts; they depended on the Kingdom of Poland for any sort of protection. The invasion began on the 15th of March, 1920, just two days after Germany's (at the time) greatest political crisis began to unfold, and while the communist-aligned Ruhr Red Army rampaged through Freikorps units and Deutsches Heer garrisons in the nation's west. As such, Germany was unable to respond in any capacity to the invasion, and had its troops retreat towards Brandenburg, East Prussia and Silesia to quell a likely communist uprising. Throughout the spring of 1920, the Red Army under the command of Leon Trotsky proved itself a capable fighting force, led in the field by legendary General Mikhail Tukhachevsky, who experimented with mechanised warfare and deep operations during this conflict. Furthermore, the Red Army had received large amounts of weapons, supplies and industrial machinery from the United States of America before, during and after the war, seeing their chance to curb German hegemony in Europe.
Jozef Pilsudski's forces were decisively defeated on the 2nd of June, 1920, in the Battle of Warsaw, during which much of Poland's best-equipped and trained units were annihilated. The German Empire declared that, if Soviet forces crossed the Vistula, it would mean war. An armistice was agreed on the 23rd, with both Eastern Poland and Galicia occupied by Soviet forces. Two days later, on the 25th, the Treaty of Brest-Litovsk was revised; the German Empire did not recognise the legitimacy of either the Ukranian SSR or the Polish People's Republic but would not engage in aggressive military action to reinstate the monarchist governments. The primary driver for such a decision was the speed with which German high command had seen the Red Army recover from World War I, the innovative tactics and strategies they had displayed, and the presence of American support for the Soviets. Victory against the Germans would be one of the drivers for the formation of the Red Orchestra and the communist wave which followed.