In 900 the Tang Empire had collapsed, heralding the demise of an East Asian world order centered on the Tang imperium. As the great aristocratic families of the Tang grappled with the end of their social and political world, new powers rose to establish regional military regimes, north and south. While the political map changed dramatically, and the social order was transformed, economic change took place in both urban and rural settings as well as along overland and maritime trading routes. The collapse of the Tang had an impact on rulers and peoples in surrounding states as well as the Korean peninsula and the Japanese archipelago. Tang China’s nomadic neighbors realigned themselves and created new polities, notably the Khitan Liao Empire. The Five Dynasties and Ten Kingdoms briefly captured the political stage following the fall of the Tang. The ruler of one of these states went on to become the founder of the Song, eventually accomplishing the political unification of north and south and laying the foundations of later imperial rule. Truce with the Khitan Liao was established by the Chanyuan Treaty in 1005, as the Tangut Xi Xia rose to threaten Song from the northwest.