Soviet-Polish relations in the inter-war period were marked by a number of formal declarations and treaties. On March 14, 1917 the Bolsheviks issued a special proclamation to the Polish Nation condemning one hundred and fifty years of Tsarist occupation and explicitly supporting Poland's right to complete independence and self-determination. On May 6, 1920 Polish legions reached Kiev, but soon afterwards the Red Armies of Tukhachevsky and Budenny began to push them back towards Warsaw. What had been known as a defensive war against Pilsudski was for a brief time transformed by the military success of the Red Army into a revolutionary crusade. The frontiers drawn by the Treaty of Riga were recognized on March 15, 1923 by the Conference of Ambassadors of the Principal Allied Powers in accordance with Article 87 of the Versailles Treaty, which authorized these Powers to fix Poland's eastern boundaries. At that time Lord Curzon was still Foreign Secretary of Great Britain.