Political map of Europe & the Mediterranean summer 242 (Gordian III’s Persian War): Pupienus and Balbinus ruled Rome for just a few months before they were assassinated by the Praetorian Guard in July 238 (Year of the Six Emperors), leaving the 13-year-old Gordian III as sole emperor. Meanwhile, Sasanian Persia continued to expand, capturing Hatra (Fall of Hatra), capital of the Roman-aligned Kingdom of Araba, in 240 or 241. From Hatra, the Persians invaded the Roman Empire itself (Siege of Nisibis (235)), leading Gordian to rally his troops and declare war in 242.