 Complete the following phrase:  During the 10th century, the Lechitic Western Polans Polanie, lit. people of the open fields turned out to be of decisive historic importance. Initially based in the central Polish lowlands around Giecz, Poznań and Gniezno, the Polans went through a period of accelerated building of fortified settlements and territorial expansion beginning in the first half of the 10th century. Under duke Mieszko I of the Piast dynasty, the expanded Polan territory was 