Complex sentence: In June 1921 an Italian Royal Commissioner was appointed, whose control lasted two weeks, whereupon a group of D'Annunzio loyalists seized part of the town, until they were in turn pushed out in September.
Split into simpler sentences: In June 1921 an Italian Royal Commissioner was appointed, whose control lasted two weeks. A group of D'Annunzio loyalists seized part of the town, until they were in turn pushed out in September.