In April, Caesar finally meets Artabanus II in battle after having conquered several provinces of the former Persian empire, including Sogdiana. The Battle of Merv is fierce and Caesar is almost defeated by Artabanus, but at the last moment is saved by a brilliant move by Scipio. Caesar is cornered between two Parthian armies and slowly being crushed between the two. Scipio begins firing flaming stones on the Parthian army closest to him. The distracted Parthians turn around and charge at Scipio’s army. Scipio fakes a retreat once again and after capturing the high ground on some hills near Merv, turns his army around and uses his cavalry and then elite legions to take out half of the Parthian army. Scipio returns to the battle field right after Caesar is wounded by a Parthian arrow. Scipio increases the Roman's morale and they attack head on, destroying the entire Parthian army and kill Artabanus II. Caesar is treated for his wounds and barely survives, but his health is affected for the rest of his life. Caesar remains with the army but gives over all command to Scipio to whom he owes his life (twice). Scipio continues to campaign south into the lands beyond the Parthian empire that Caesar conquered, further cementing Roman control in those areas. The Battle of Aria effectively secures the Roman eastern border and by the end of the year Scipio begins building massive defenses along the entire border and the Via Scipia. Scipio remains in Parthia until 18 B.C. building massive permanent forts and defenses along the Indus and Amu Darya Rivers. Caesar returns to Rome in bad health. All of Parthia is annexed to Rome in September after treaties are concluded with the remaining Parthian satraps. One family in particular, the remaining members of the Parthian royal family, and Phraates V’s brother, Vonones, conclude the treaty with Rome and will be very important to Roman history later.