english: When Emperor Qin Shi Huang unified the states in 221 BCE, the Tibetan Plateau and Pacific Ocean became natural barriers, but the mountains in the north remained vulnerable to Mongol, Turkish, and Xiongnu invasions.
non_english: Kad je car Ćin Ši Huang ujedinio države 221. godine pre n.e. Tibetanska visoravan i Tihi okean postali su prirodne prepreke, ali planine na severu ostale su podložne napadu Mongola, Turaka i plemena Hsiung-nu.