 The Tang capital, Chang'an, was a major economic and cultural hub, and was the world's largest urban settlement at the time.The Silk Road facilitated economic and cultural exchanges between China and the outside world, with Persians and Sogdians among those who benefited the most from such exchanges with China.In the north, the First Turkic Khaganate was defeated and annexed; in the west, the Tang dynasty extended its control as far as modern-day Afghanistan and the Aral Sea; in the east, Tang control reached Sakhalin.