Answer:
Trajan (reigned 98 - 117 CE)
Step-by-step explanation:
During the rule of Trajan, that lasted from 98 to 117 AD, the Roman Empire reached its greatest territorial expanse with 5 million square miles. Trajan had campaigned against Dacia (now Romania and Moldova), in Arabia and added parts of Armenia, Mesopotamia, and Babylon to the Roman Empire.