"Poland is a major exporter of great Americans, great Israelis, and great Russians."—Anonymous
"For centuries, Poland has been known specifically for two things: badass spicy sausages, and getting epically fucked over by every other European nation in every possible way."
Poland. The picked-on kid with glasses of the European school playground, but it hasn't always been.
Poland arose when the West Slavic tribes of the region were united by the Polans around about 1000. Perhaps the most globally notable event of first two or three centuries of Poland's existence was when one of Polish princes invited The Teutonic Knights to help him against the pagan Prussians. It later became quite a nuisance, so to say. Poland, looking for allies, became associated with Lithuania (also having a problem with the Knights) and together they broke the power of the Order. Over time Lithuania eventually merged with Poland, forming the Polish-Lithuanian Commonwealth (a kind of The Federation and The Kingdom at once). Together, Poland and Lithuania ruled over an enormous empire and were immensely powerful. Above all, this period is remembered for "Golden Liberty", when kings were elected and one in ten people could vote, more than anywhere else in Europe at the time. The King had to share power with the Sejm, or senate. The Commonwealth was also known for its religious tolerance (letting, for instance, Jews live more or less in peace when most countries reveled in senseless persecution), at a time when religious wars were consuming the rest of Europe. At its height, the Polish-Lithuanian Commonwealth was the largest country by land area in Europe. The Commonwealth in this period is also known for fielding the completely Badass winged hussars.
Golden Liberty was a great inspiration for the American Revolution, but it had a flaw, to which we owe the existence of a strong US Presidency: any one noble could block laws (the Liberum Veto with which Europa Universalis players may be familiar), so as soon as one person got bribed by Russia, Prussia, or Austria, the country was in their hands. The Poles got tired of this at about the time of Washington and passed a new constitution, very progressive for the day (the second written constitution in history, inspired by the American constitution). Russia, Prussia, and Austria, the "three black eagles", decided that enough was enough and abolished the country.
Poles in Austria generally enjoyed the right to speak their language and quite a bit of self-rule, and were fairly supportive of the Habsburgs (even today, Emperor Franz Josef is remembered fondly in southern Poland, while praising other rulers of the "three black eagles" would make Poles twitch). Poles in Prussia were originally well-treated (Frederick the Great required the heir to the throne to be fluent in Polish, although this was never really implemented). After the Napoleonic War, borders were shuffled and the smaller number of Poles left in Prussia were mostly in ethnically-mixed areas such as Upper Silesia and found their circumstances hard, especially after the abolition of their autonomy in 1848. Political hardship only led to a strengthening of Polish national spirit, but economic hardship compelled many Polish Germans (or German Poles) to move to the thriving Rhineland or over the Atlantic.
Poles in Russia had it bad. Not surprising, then, that they tried to change the situation twice (twice-and-a-half including the rioting during the Revolution of 1905). The first time, the November Uprising, they actually had the means to change the situation, as the Russian part of Poland was technically autonomous and in personal union with Russia, and as such had a rather manageable army. Not surprisingly, the second uprising, the January Uprising, was restricted to guerilla warfare and ended in tragedy, the abolition of Polish autonomy, and many Poles being sent to Siberia. 
So during WW 1, many Poles, including future leaders such as Pilsudski and Sikorski, joined Austro-Hungarian forces (though there was a Russian-loyal faction, led by a Nationalist leader Roman Dmowski) and helped the Central Powers to establish a puppet Polish Kingdom in former Russian territory, as the lesser of two evils. If sent to the western front, they usually deserted to join the French Foreign Legion. After the war, a new independent Poland was created, and had its moment of glory saving the world from Reds with Rockets against really, really bad odds.
Things then started taking turns for the worse. Immediately after the collapse of the Russian Empire resulted in the renewed independence of most of the former Commonwealth, Poland laid claim to the Lithuanian city of Vilnius, leading to a war between the former allies. The Ukrainians who had invited the Poles in to rescue them from the Reds found that Warsaw had none of their best interests at heart (Piłsudski personally was very ashamed by this). Their German minority were also treated in a rather nasty way. Poland was making powerful and numerous enemies, its industrialization was slow and faltering, and its internal tensions came to the fore when the military staged a coup and established the "Government of Moral Sanitation".
During the War, Poland suffered possibly the most brutal occupation in the world. The Holocaust was carried out there, and it was the official intention of the Nazis to plunder Poland and starve it to death. Contrary to popular wisdom, the Poles fought brilliantly against overwhelming odds, never surrendered, and even when stabbed in the back by the Commies, escaped to fight another day. The cavalry charging tanks was a myth; the incident that inspired this story involved a Polish cavalry division (actually mounted infantry, like most cavalry of the time, though with traditions and training) which routed a German infantry division but was counter-attacked by armoured cars. Additionally, while some Polish cavalry units did deliberately engage German armor, they did so dismounted while wielding anti-tank rifles.
The Poles didn't take occupation lying down. As well as organising a resistance movement, tens of thousands of Polish men escaped from the country and made their way to Britain and France to continue the fight, forming entire squadrons of airmen and divisions of ground troops. By the end of the war, there were ~250 thousand Poles fighting alongside the Western Allies, with another ~200 thousand aiding the Soviets. Suffice it to say that Poland had more than its fair share of Awesome Moments during the period.
Poland lost a fifth of its population in the war- seven million people in all, mostly civilians. Out of a pre-war Jewish population of 3.3 million, only 300,000 survived (Poland's Jewish population were Polish citizens; Israel did not exist until after the war.)
After the war, the country was taken over by the Reds with Rockets, who kicked millions of Poles out of their ancestral homes, depositing them in former Eastern Germany, where they in turn kicked millions of Germans out of their ancestral homes, thus accounting for the country's suspiciously straight borders (the western border follows the line of the Oder and Neisse rivers) and the fact that Warsaw, originally chosen as the capital for its central location, is no longer especially central. Stalin was not a nice guy. Poland suffered long and hard under deeply incompetent Communist rule, and eventually Polish people were instrumental in its downfall.
Home of the trade unionist with the impressive moustache (who became President) and formerly had identical twins as its President and Prime Minister. Also home of a very famous and popular former pontiff.
- Polish Educational System
- Poles With Poleaxes (the Polish military)
- Polish Jews
- Polish Soviet War
- Siege of Vienna
- The Teutonic Knights
Famous Real Life Poles:
- Lech Wałęsa
- Pope John Paul II
- Roman Polanski
- Marie Curie - nee Maria Skłodowska.
- Nicolaus Copernicus - quite probably he was ethnically German, but was a loyal subject of the Polish king.
- Fryderyk Chopin - his father was a Frenchman, but he was very much a Pole.
- Zbigniew Brzezinski, Carter's advisor.
- Stanislaw Lem - SF author, suspected by Philip K. Dick not to exist.
- Philip K. Dick suspected him of being a group of KGB agents, to be accurate.
- Pawel Edmund Strzelecki - an explorer of large swaths of Australia and a person who named the continent's tallest mountain after...
- Tadeusz Kosciuszko - A revolutionary and Badass enough to be a national hero in four countries - Poland, Lithuania, Belarus, and USA (he founded West Point).
- Joseph Conrad, whose given name was Jozef Korzeniowski. Wrote in English.
- Zdzisław Beksiński - Surrealist painter
- Ernest Malinowski - An engineer. Constructed at that time the world's highest railway Ferrocarril Central Andino in the Peruvian Andes in 1871-1876.