The Miracle On The Vistula
On 15 August 1920, the Polish Army launched a counter-attack against the Red Army which stood at the gates of Warsaw. They succeeded to such a degree that the Soviets were rolled back and Poland gained twenty years of independence.
The Polish victory was even more important to the West. A Russian victory at Warsaw would have brought the Red Army into Germany. The Cold War would have begun in 1920 with the Iron Curtain starting at the Rhine. Despite the importance of the battle, the Poles fought it alone-- the French and British were hamstrung by domestic politics and did next to nothing to aid the defense.
In fact, British unions were defiantly pro-Soviet. During the Russo-Polish War they sometimes refused to load ships with military goods bound for Poland.