• 1385-1386 The Polish nobility marries Queen Jadwiga, then aged 12, to Lithuanian Grand Duke Wladislaw Jagiello. Jagiello converts to Catholicism as a condition of this union, which also unites the two countries. Ongoing incursions from the Knights of the Teutonic Order (the villains of Sergei Eisenstein's Alexander Nevsky) are a major incentive.
• The Teutonic Order's Northern crusades are the apparent reason that Poland (the Danzig corridor) was between two parts of Germany through 1939. The Order vanquished and then Christianized or ethnically-cleansed the original Prussians, who were pagans. This introduced German culture and language to the southern Baltic region. Prussia itself was a vassal of the Commonwealth for quite some time. It's surprising that no one undermined Hitler's vicious racial theories with the argument that a good many "racially inferior" Poles were doubtlessly part German while a good many of Hitler's "supermen," especially those in Prussia itself, were almost certainly part Slavic.
  
• 1410: King Jagiello defeats the Teutonic Knights at the Battle of Grunwald (Tannenberg). In Henryk Sienkiewicz's With Fire and Sword, this is where Pan Longin Podbipyenta's ancestor beheads three "hooded knights" (Teutonic knights were a monastic order, something like the Templars) and earns the name "Hoodsnatcher."
• 1569: the Act of Union at Lublin unites Poland and Lithuania into one country.
• 1605: Battle of Kircholm. 3000 Husaria wipe five times their number of Swedish musketeers and pikemen off the face of the earth.
• 1683: Relief of Vienna. King Jan Sobieski defeats a Turkish army that is at the gates of Vienna.
  

Political and Scientific Innovations (Principal reference: Adam Zamoyski, The Polish Way)

• Libertarianism
• "...dislike of authority for its own sake, the rejection of any theory that the public good could be served by exerting pressure on the individual, and the belief in the inalienable rights and dignity of the individual" had been part of Polish culture since the Middle Ages. (Zamoyski, p. 104)
  
• Freedom of Religion: "[the Kings of Poland] graciously allowed their subjects to do anything they wanted- except butcher each other in the name of religion."
• One Bishop of Krakow told his parishoners, "I don't care if you worship a goat as long as you keep paying your tithes!"
• The Commonwealth attracted numerous Jewish refugees from the Spanish Inquisition. At least one became a member of the szlachta (gentry), and others served in the Commonwealth's armed forces. (Henryk Sienkiewicz's Colonel Wolodyjowski mentions a Jewish gunner at the siege of Kamenets.)
• No Inquisitions allowed: in 1554, the Bishop of Poznan sentenced three burghers to be burned at the state for heresy. A posse of mostly Catholic szlachta rescued them. The same bishop tried to burn a cobbler at the stake but more than a hundred szlachta of all faiths showed up to prevent this. The Sejm soon recognized the danger of ecclesiastical courts and revoked their authority to try anyone for anything in 1562.
• In 1572, five Catholics were beheaded for participation in a riot that burned down the Calvinist chapel in Krakow. (The punishment was obviously not for a religious crime in a Catholic-majority country, but rather for arson.) The predominantly Catholic city raised money to build a new church for the "heretics," and the Bishop himself contributed a generous sum.
• An act of the Sejm in 1573 (the Confederation of Warsaw): "Whereas in our Common Wealth [sic] there is no small disagreement in the matter of the Christian faith, and in order to prevent that any harmful contention should arise from this, as we see clearly taking place in other kingdoms, we swear to each other... that albeit we are dissidentes in religione, we will keep the peace between ourselves, and that we will not, for the sake of our various faith and difference of church, either shed blood or confiscate property, deny favour, imprison or banish, and that furthermore we will not aid or abet any power or office which strives to this in any way whatsoever..." (Adam Zamoyski, The Polish Way, 90-91).
• In the movie verion of Henryk Sienkiewicz's Colonel Wolodyjowski, Catholics take the worship of Muslim Tartars (kneeling toward Mecca) as an everyday occurrence.
  
• Freedom of the Press
• "While originally legislation demanded that all books be passed by the Rector of the Jagiellon University, the executionist movement won a notable victory in 1539 by obtaining a royal decree on the absolute freedom of the press" (Zamoyski, p. 117).
  
• Right to Keep and Bear Arms
• Although the Commonwealth's laws didn't seem to have anything like the Second Amendment, Polish literature shows that commoners (e.g. peasants) as well as gentry (szlachta) were free to own weapons. The szlachta were, in fact, almost subject to anti-gun-control laws. Custom obliged them to fight for the country in times of need and they were expected to provide their own swords, firearms, armor, and horses. The exception was the Hussar lance or kopia which was very expensive and tended to break with a solid hit, so it was provided by the government.
  
• In the movie version of Henryk Sienkiewicz's The Deluge, the King of Poland (Jan Kazimierez) runs into a large number of Swedes. The King's escort, including Andrei Kmicic, do their best to defend him but there are too many Swedes. That's when Polish peasants emerge from the surrounding forest, jump the Swedes, and save the King. Many of the peasants had firearms. This underscores the role of privately-owned weapons in national defense.
• Communism (from a "fringe" element, not mainstream Commonwealth culture)
  
• The Arian or anti-Trinitarian Christian sect was, like other non-Catholic religions, tolerated in the Commonwealth. They believed in the communal ownership of all material goods, and the word "communist" was used for the first time in 1569.