Chao was one of the first known ministers to suggest to Emperor Wen that Han armies should have a cavalry-centric army to match the nomadic Xiongnu to the north, since Han armies were still primarily infantry, with cavalry and chariots playing a supporting role. He advocated the policy of "using barbarians to attack barbarians," that is, incorporating surrendered Xiongnu horsemen into the Han military, a suggestion that was eventually adopted, especially with the establishment of dependent states of different nomads living on Han's frontiers. Like Jia Yi (201–168 BC), he was an early proponent of terminating the "heqin" marriage alliance and tribute treaty with the Xiongnu, although he opposed it for practical reasons rather than Jia's staunch ideological position that superior sedentary Chinese culture should dominate over the northern nomads. The "heqin" agreement was supposed to guarantee peace and stability between the Han and Xiongnu. Chao believed that the "heqin" agreement had been breached and ignored by the Xiongnu on so many occasions—with continuous raiding and plundering along Han's borders by Xiongnu tribe and clan leaders—that the treaty simply failed to live up to its goals and lost all practical use. It was not until after the Battle of Mayi (133 BC) during Emperor Wu's reign (141–87 BC) that the "heqin" treaty was finally abolished in favor of an offensive military strategy to break apart the Xiongnu Empire.