Speaking of Poland, if ever a people deserved the title "Unsung Heroes", it would have to be the Poles. Their country lies across a large flat area of land that forms a natural east-west thoroughfare into Europe, and at least twice in recorded history they have saved Western Civilisation.
The first was in 1683, when following a successful campaign against allies of the Ottoman Turks on their eastern borders, Polish-Lithuanian forces under Jan Sobieski lifted the Siege of Vienna. That ended Ottoman expansion into Central Europe, and began the slow decline of the Ottoman Empire.
The second time was in 1920, when the communist armies of the fledgling Soviet Union stood poised on Poland's River Vistula. Flush with victory over its counter-revolutionary enemies (and also, up until that time, the Poles), the Red Army expected to next strike deep into a war-weakened Germany. From there, Lenin expected his forces to press rapidly onwards through an equally war-weakened France and extend communist revolution right up to the English Channel. However, the Polish armies under Jozef Pilsudski rallied at the Vistula and inflicted on the Red Army such a devastating defeat that it fled in disorder, well back into Russian territory. (For an informative description of these events, Denis Wheatley's Red Eagles is quite an informative read. While Wheatley does tend to over-praise the military genius of the Russian Southern Front Commander, Klim Voroshilov, his account of the Battle of the Vistula is quite accurate).
Were it not for these two events, the course of western history could well have been quite different. (e.g. the "Iron Curtain" may have appeared a generation earlier than it did, and run along the shores of the English Channel and North Sea!)