In AD 17 or 18, Tiberius had trimmed the ranks of the Praetorian Guard responsible for the defense of the city, and had moved it from encampments outside of the city walls into the city itself, giving Sejanus access to somewhere between 6000 and 9000 troops.
Dalam 17 M atau 18 M, Tiberius telah dipangkas jajaran Praetorian menkadi penjaga bertanggung jawab atas pertahanan kota, dan pindah dari perkemahan di luar tembok kota ke kota itu sendiri, memberikan akses Sejanus ke suatu tempat antara 6000 dan 9000 tentara.