Destruction of the Tran aristocracy

The fortunes of the Ly and Tran dynasties waxed and waned in step with the Song and Yuan dynasties. There was a vital connection between regimes in the Red River plain and the successors to the northern dynasties that had governed there during earlier centuries. Both sides carefully observed the tributary relationship. Books, medicine, theater, music, weapons, and government policies in the north were easily perceived, understood, and adopted in the south. Disorders and political troubles in the south were monitored and any potential for requiring or enabling intervention was evaluated in the north.

In both the Song–Ly cycle and the Yuan–Tran cycle, the rise of the northern dynasty was accompanied by the rise of the southern dynasty, and the decline of the northern dynasty was accompanied by the decline of the southern dynasty. The relative sizes of the two sides ensured that initiative in the relationship came from the north. The role of the south was to answer northern initiative. Moments of warfare climaxed both cycles, the outcomes of which confirmed the general basis of the relationship between vassal and suzerain. The ebbs and flows of power and prosperity in the north and in the south reveal that, in the eleventh and thirteenth centuries, northern challenges evoked southern responses. Similarly, in the twelfth and fourteenth centuries, northern weakness gave slack to the relationship and led to weakness in the south.