Complex sentence: Following Domitian's murder, the Senate rapidly appointed Nerva to hold imperial dignity--this was the first time that senators chose the emperor since Octavian was honored with the titles of "princeps" and "Augustus".
Split into simpler sentences: Following Domitian's murder, the Senate rapidly appointed Nerva to hold imperial dignity. This was the first time that senators chose the emperor since Octavian was honored with the titles of "princeps" and "Augustus".