Reconquest By Aurelian
In 270, Aurelian became Roman Emperor. After defeating the Alamanni, who were threatening to invade Italy, Aurelian turned his attention to the lost eastern provinces - the Palmyrene Empire.
Asia Minor was recovered easily; every city but Byzantium and Tyana surrendered to him with little resistance. The fall of Tyana lent itself to a legend; Aurelian to that point had destroyed every city that resisted him, but he spared Tyana after having a vision of the great philosopher Apollonius of Tyana, whom he respected greatly, in a dream. Apollonius implored him, stating: "Aurelian, if you desire to rule, abstain from the blood of the innocent! Aurelian, if you will conquer, be merciful!" Whatever the reason, Aurelian spared Tyana. It paid off; many more cities submitted to him upon seeing that the emperor would not exact revenge upon them.
Aurelian defeated Queen Zenobia in the Battle of Immae and again, decisively, in the Battle of Emesa. Within six months, his armies stood at the gates of Palmyra, which surrendered when Zenobia tried to flee to the Sassanid Empire. The Palmyrene Empire was no more.
After a brief clash with the Persians and another in Egypt against usurper Firmus, Aurelian returned to Palmyra in 273 when it rebelled again. This time, Aurelian allowed his soldiers to sack the city, and Palmyra never recovered from this. He was known as Parthicus Maximus and Restitutor Orientis ("Restorer of the East").
Read more about this topic: Palmyrene Empire