I would like to rectify the Polish nationalist version of the history of Royal Prussia posted by Domen.
Royal Prussia was part of the Kingdom of Poland since 1466, but until 1569 it had autonomy. In 1569 it was not incorportaed to the Kingdom of Poland (as it already was its part), but to the Crown of Poland, which was only part of the entire kingdom.
Here is a quote from Andrzej Kaminski, "Polish-Lithuanian Commonwealth and its Citizens", in the book "Poland and Ukraine Past and Present". It is an example of non-chauvinist history written by a Pole, as opposed to the chauvinist version of Polish history.
When the union with Lithuania was signed [in 1569], the rich province of King's Prussia was also incorporated
[into the Kingdom of Poland]. Belonging to the Crown since 1466, its political system was more like Holland's than like Little Poland's. Cities played the predominant role in the political life of Prussia by controlling the provincial Diets and cooperating with the group of magnates who were the local county officials. The sovereign authority in the province had been the general Diet of Prussia. The King as supreme sovereign was limited by laws and did not participate in the Prussian Diet. In turn, the Prussian Diet had vehemently refused to participate in the Polish Diet since it did not wish to recognise the latter's authority. But because the Prussian nobility was dominated on its own territory by the patriciate of the three large cities - Gdansk, Torun and Elblag - it entreated the royal officials to end the separatism of its province. A combination of the "Respect for the Law" movement, royal pressure, and the liberation of the Prussian nobility led to the incorporation of Prussia into the Polish Crown.
The source quoted by Kaminski for the above is W Odyniec, Dzieje Prus Krolewskich 1454-1772
(Warszawa 1972), pp. 102-140.
Note that Kaminski says that the political system in Royal Prussia was more like that of Holland than of Little Poland, the centre of the Polish Kingdom, and was based on cities. The reason for that difference was the presence in Royal Prussia of a very large German population, which was heavily urbanised and politically and culturally more advanced than the more rural Polish population, consisting of nobles and peasants.
To be of Prussian nationality (which was by the way not very numerous in 16th century as almost all Prussians were exterminated or Germanized) Copernicus would have to be born to a Prussian family, while he was born to a Polish-German couple.
By the 15th Century, when Copernicus was born, the term "Prussian" was applied to all the inhabitants of Prussia, both Royal (West) Prussia and Ducal (East) Prussia. It no longer denoted solely the descendants of the original Old Prussians, who were by that time no longer distinguishable from the settlers who had colonized their territory.
Since Copernicus was born in Royal prussia, he was a Prussian, the point made by Norman Davies.
The point is that the meaning of a national name can change over time. Take for example the term "British", or "Briton". Today those terms denote inhabitants of Britain, who speak English, a Germanic language. However, in Roman times the terms denoted a people speaking a celtic language, who were later conquered and expelled or absorbed by the invading English.
Even in Shakespeare's time, the word "British" was used to denote only the ancient inhabitants of Britain, in Roman times; the Englishmen of his time never called themselves "British".
The modern use of the word "British" dates from the early 18th Century, when England and Scotland were united to become the United Kingdom; the word "british" was adopted to cover both the English and Scottish peoples.
Thus the term Prussian, which originally denoted an ancient tribe speaking a Baltic language akin to Lithuanian, later came to be applied to all the people living in the territory known as Prussia (both German and Polish-speaking), and finally came to denote only Germans.
In 1308 Brandenburg invaded Gdansk Pomerania and captured Gdansk, which belonged to the Kingdom of Poland then. The Polish king called for help of the Teutonic Order to help him to repulse Brandenburgian forces from his territory. Teutonic Order defeated Brandenburgians but instead of returning the city to Poland, captured Gdansk on their own and slaughtered its population. One year later in 1309 Teutonic Order captured also the rest of the Polish Gdansk Pomerania. As the Polish king was involved in other areas, he had no forces to take back his property and so Gdansk Pomerania remained in Teutonic hands despite numerous complaints to the pope by the Poles. So in 1309 Gdansk Pomerania became part of the Teutonic Order in Prussia.
The above is a rather chauvinist version of history, presenting the conquest of Danzig as an ethnic conflict between Germans and Poles. In fact it was the result of a conflict between rival Polish nobles for the crown of Poland.
In 1308, the claimant to the crown of Poland who actually held sway in the Polish capital, Krakow, was Wladyslaw Lokietek, who lived from 1260 t0 1333 He had seized power in 1305, after the resignation of Vaclav, who was also king of Bohemia. However, Lokietek's claim was disputed by other claimants.
Lokietek had been ruler of Poland twice before. He had first become Prince of Poland in 1289, but had been expelled by Przemyslaw, Duke of Poznan in 1290, who was the first to be crowned King of Poland. Lokietek had been restored in 1296, calling himself King Wladyslaw I, but had again been expelled in 1300 by Vaclav, King of Bohemia, who was then elected King of Poland. In 1305, Lokietek became ruler for the third time. As can be seen, his claim to the crown was very shaky and in dispute.
In 1308, the Duke of Pomerelia, the area where Danzig was located, laid claim to the Polish crown, and asked the Elector of Brandenburg for support; in return he offered to give the Elector possession of Danzig. In due course the army of the Elector of Brandenburg arrived at the gates of Danzig; the citizens of Danzig, mainly German, opened the gates and allowed the Brandenburg army to take possession. Only the Danzig citadel, held by a force loyal to Lokietek and under the command of his castellan Bogusza, refused to surrender; it was then besieged by both the Brandenburg army and the citizens of Danzig.
Since Lokietek had no forces to send against the Elector of Brandenburg and the Duke of Pomerelia, he asked the Grandmaster of the Teutonic order to do the job for him. The Grandmaster agreed, on condition that Lokietek would reimburse the Teutonic Order for all its costs incurred in conquering Danzig and Pomerelia for him; until that debt was paid, the Knights would keep possession of the territories they conquered as collateral.
The army of the Teutonic Knights then attacked Danzig and drove away the Brandenburg army. Since the citizens of Danzig had rebelled against the King of Poland, they were to be punished by death; the Teutonic Knights carried out the executions on behalf of King Wladyslaw Lokietek. Most of the slain citizens were ethnically German, since the majority of the Danzig citizenry was German at that time.
Thus, the capture of Danzig by the Teutonic Knights and the massacre of the citizens was not a case of germans capturing a Polish city and killing its Polish inhabitants, but rather a case of German knights killing German townsmen on behalf of a Polish King.
The following year, he Teutonic Knights conquered the rest of Pomerelia, again on behalf of the Polish King. However, when it came time for King Wladyslaw Lokietek to pay his debt to the grandmaster and take possession of the lands the Knights had conquered for him, the Grandmaster pulled a swifty on him presenting a bill of costs so high that Lokietek simply could not pay it. As a result, the Teutonic Knights retained possession of Danzig and Pomerelia as settlement for the unpaid debt.