but in reality, they hold most power of the royal court and de facto rulers of the northern half of Đại Việt, and began using the title Chúa (lord), which is outside of the classical hierarchy of nobility. The Le king was reduced to a figurehead, he ruled in earnest, while the Trịnh lord had total power to select and enthrone or remove any king the lord favors. The southern Nguyễn leader also began to proclaim as Chúa lord in 1558. Initially, they were considered subjects of the Le court, which was controlled by the Trịnh lord. But later, by the early 1600s, they ruled southern Đại Việt like an independent kingdom and became the main rival to the Trịnh domain. Le Thanh Tong's legacy such as his 1463 Code and bureaucratic institutions, was revived in the north and somehow continued to persist and lasted until French Indochina period. Before and after the war, the two Thanh Hoá clans divided the kingdom into two simultaneously coexist but rival regimes: the northern Đàng Ngoài or Tonkin ruled by the Trịnh family while the southern Đàng Trong or Cochinchina ruled by the Nguyễn family; their natural border is the city of Đồng Hới (18th parallel north). Each polity had its own independent court, however, the Nguyễn lord still sought to subordinate himself with the Lê dynasty, which also stayed under Trịnh supervision, trying to pretend an imaginary unity. Paying homage and respect to the Le king remained a source of both lords' legitimacy and of adherence to the idea of a unified Vietnamese state, even if such a thing no longer existed or was loosely emptied. The Tay Son rebellion of the late 18th century Đại Việt was an extraordinary movement of Đại Việt's chaotic period when the three Tay Son brothers divided the kingdom into three subordinating but independently realms ruled by them who all declared kings: Nguyen Hue controlled the north, Nguyen Nhac controlled the central, and Nguyen Lu controlled the Mekong Delta. Economy Fan Chengda (1126–1193), a Chinese statesman and geographer, wrote an account in 1176 that described the medieval Vietnamese economy: Unlike southern neighbor Champa, medieval (900-1500 AD) Đại Việt was mostly an agricultural kingdom, centered around the Red River Delta. Most stelae epigraphs discussing the economy from this period concerned land reclamation, maintaining irrigation system of the Red River, culminating fields, harvesting, and the king's land donation