royal court and governed by the Zhou kings from the capital, but with peripheral non-Han tribes on the outer borders and Han Chinese in the center. The term "Ten Thousand States" () refers to both territory and the subjects who reside therein, both Han and "barbarian". The Zhou kings received and empowered these "Ten Thousand States" by virtue of the Mandate of Heaven. This is some of the earliest evidence of the Hua–Yi distinction. During the Spring and Autumn and Warring States periods in the latter half of the Zhou dynasty, the power of the feudal lords developed rapidly, and several non-Han regions became powerful states themselves. As many of these feudal states had shared cultural and economic interests, the concept of a great nation centered on the Yellow River Plain gradually expanded. The term tianxia began to appear in classical texts such as the Zuo Zhuan and Guoyu. The territory and governments of the Zhou dynasty and the Qin dynasty were unified after the conquests of Qin Shi Huang, and the concept of tianxia was adapted to act as an actual geographic entity. Qin Shi Huang's goal to "unify all under Heaven" was, in fact, representative of his desire to control and expand Chinese territory. At the founding of the Han dynasty, the equivalence of tianxia with the Chinese nation evolved due to the feudal practice of conferring land and autonomy upon the aristocracy to avoid having to expend military expense in their subjugation. Although many areas enjoyed great autonomy, the practice established and spread Chinese language and culture throughout an even wider territory. Unification theme applied to tianxia can be seen in Sun Tzu's The Art of War where the supreme goal of offensive strategy was to conquer without destroying that which you sought to conquer: Unified China fractured into many different dynasties during the Southern and Northern dynasties period, and with it went the practical use of the term tianxia. In the 7th century during the Tang dynasty, some northern tribes of Turkic origin, after being made vassal, referred to the Emperor Taizong as the "Khan of Heaven". By the time of the Song dynasty, northern China was ruled by the Khitan-led Liao dynasty, the Jurchen-led Jin dynasty, and the Tangut-led Western Xia dynasty. After being threatened by these northern states and realizing the possible effects of a war to the country and people, the Song rulers