Complex sentence: A Prussian king first set foot on the Rhine in 1609 by the occupation of the Duchy of Cleves and about a century later Upper Guelders and Moers also became Prussian.
Split into simpler sentences: A Prussian king first set foot on the Rhine in 1609 by the occupation of the Duchy of Cleves. About a century later, Upper Guelders and Moers also became Prussian.