Birtha (Mesopotamia) bastions are quite traceable. There are the ruins of a vaulted secret staircase, leading down from the heart of the citadel to the water's edge. Birtha (Mesopotamia) Birtha () was an ancient fortress on the river Tigris, which was said to have been built by Alexander the Great. It would seem, from the description of Ammianus, to have resembled a modern fortification, flanked by bastions, and with its approaches defended by out-works. Shapur II here closed his campaign in 360, and was compelled to retire with considerable loss. D'Anville and Edward Gibbon both identify Birtha as modern-day Tikrit, Iraq. The
Mesopotamia (Roman province) Mesopotamia (Roman province) Mesopotamia was the name of two distinct Roman provinces, the one a short-lived creation of the Roman Emperor Trajan in 116–117 and the other established by Emperor Septimius Severus in ca. 198, which ranged between the Roman and the Sassanid empires, until the Muslim conquests of the 7th century. In 113, Emperor Trajan (r. 98–117) launched a war against Rome's long-time eastern rival, the Parthian Empire. In 114, he conquered Armenia, which was made into a province, and by the end of 115, he had conquered northern Mesopotamia. This too was organized as a province in early