Two superpowers in the 8th century AD: the Caliphate and Tang dynasty
In classical times, the great Roman Empire and the Han Dynasty never met.
But in the Middle Ages, the two greatest empires of the East and West clashed head-on.
Two empires exceeding 10 million square kilometers
These were the two most powerful empires of their time, representing the pinnacle of military, economic, cultural, and artistic achievement.
The Arabs conquered to the east, the Chinese conquered to the west.
The Caliph's greatest military achievement: conquered the Sasanian Persia
The Tang Dynasty's greatest military achievement: conquered the Eastern and Western Turkic Khaganates
There were approximately 9-10 military conflicts, the most famous being the Battle of Talas. The Turgesh, originally a vassal state of Chinese, rebelled during the war, leading to a Chinese defeat.
However, the Turgesh did not fare well either; they were subsequently retaliated against by the Chinese, and their state was destroyed.
（As it turned out, traitors rarely had a good ending. The Arabs also disliked these people who temporarily defected during the war. They even joined forces with the Chinese to attack them from both sides ）