The national defense policy of Han Empire had focused on resisting the invasion of Xiongnu since Emperor Gaozu’s escape from the envelopment in the Battle of Baideng. Emperor Gaozu initiated the policy of heqin, which involved sending noble ladies to marry the Xiongnu leaders and paying annual tribute to the Xiongnu in exchange for peace between the Han Empire and the Xiongnu. Although the policy of heqin was debated and even censured by some ministers of great vision, poor economy held back Han Empire’s active military strategies until the Rule of Wen and Jing. The Rule of Wen and Jing enabled Emperor Wu to maintain a powerful army and employ an aggressive military strategy, which in turn dramatically expanded the empire and ultimately pushed the Han dynasty to its zenith.