The early 1500s brought in the Renaissance and, despite the smaller size of the kingdom, became one of Poland's most prosperous times. The country became a destination for scholars and businessmen and had more Jews within its boundaries than the rest of Europe combined by 1600. Also during this time, in 1569 the capital was moved to Warsaw, which marked the beginning of instability and decline, first signified by the Swedish invasion in 1655, then in the late 1700s the country was partitioned by their three neighbors, Russia, Prussia, and Austria. Each part of Poland progressed according to their occupier. The lands under the rule of the Austrians were free to trade and continue a fairly Polish lifestyle, while at the other extreme, the Russians forced the Russian language and repressive economic laws on their Polish territories.
World War I's eastern front was almost entirely fought on Polish soil as the war pitted the Russians against the Germans and Austrians, whose land met in what was formerly Poland. The Poles were recruited into armies and forced to fight, but it seems only the Poles in the Austrian-controlled region liked their occupier enough to actually fight for them. As the war came to a conclusion, Polish lobbyists in the U.S.A. convinced the winning allies to recreate a Polish state in 1918.
The interwar period consisted of trying to become politically and economically stable, but as this was still a distant reality, Poland found itself in between the Soviet Union and Germany, who were ready to invade. In 1939 Germany invaded Poland and World War II began. Poland found itself being "cleansed" of its people; both the Jews and the intellectuals who the Germans viewed as a threat. Nearly every Jew in Poland was killed in death camps and many more ethnic Poles were killed there as well, while the Soviets shipped still additional Poles to their Gulag, many of which is in addition to the losses on the battlefields, which in total cost the lives of six million people, or nearly 20% of Poland's population.