Complex sentence: King George I of England was opposed to the marriage because he feared that there would be an heir and, in order to placate him, the Austrian Emperor, Charles VI arrested Princess Maria Klementyna while on her way to Italy to marry James Stuart.
Split into simpler sentences: King George I of England was opposed to the marriage because he feared that there would be an heir. In order to placate him, the Austrian Emperor, Charles VI arrested Princess Maria Klementyna while on her way to Italy to marry James Stuart.