I am interested in what was going on in Poland around this time that might have caused him to leave.
Here is an excerpt from Wikipedia: "Partitions of Poland
Main article: History of Poland (1795-1918)
Poles would resent their fate and would several times rebel against the partitioners, particularly in the nineteenth century. In 1807 Napoleon recreated a Polish state, the Duchy of Warsaw, but after the Napoleonic wars, Poland was again divided in 1815 by the victorious Allies at the Congress of Vienna. The eastern portion was ruled by the Russian Czar as a Congress Kingdom, and possessed a liberal constitution. However, the Czars soon reduced Polish freedoms and Russia eventually de facto annexed the country. Later in the nineteenth century, Austrian-ruled Galicia, particularly the Free City of Kraków, became a centre of Polish cultural life."
As you can see Poland was partitioned during this time. Poznań and Inowroc³aw were under Prussian rule (this is probably why you refer to Poznań by its German name of Posen). A lot of Poles left Poland due to foreign rule over the country. Here is another excerpt from the wikipedia: "The Province of Posen (German: Provinz Posen, Polish: Prowincja Poznańska) was a province of Prussia from 1848-1918 and as such part of the German Empire from 1871 to 1918; the whole area is now part of Poland. Its capital was Poznań (German: Posen). The province replaced the Grand Duchy of Posen." You may want to start your reading right there: en.wikipedia.org/wiki/Province_of_Posen