What is the theme in Poland by James A. Michener?

One of the dominant themes of the book is nationalism. It is not only the nationalism of the Poles throughout their history, but also the nationalism of the other ethnic groups in the country. The Poles and other peoples in the area have strong ties to their history and culture yet have been subject to foreign domination at various periods in their history. Poland has been subject to the invasions and rule of the Tartars, Swedes, Germans and Russians. They had no strong leader throughout most of their history since the Polish kings were foreigners who were hired by the magnates. The magnates didn't want to see their power diminished by a strong government of any kind.