At the start of Emperor Wu's reign, the Han empire had a
standing army comprising 400,000 troops, which included 80,000 to 100,000 cavalrymen, essential to the future campaigns against the Xiongnu.
[121] However, by 124 BC, that number had grown to a total of 600,000 to 700,000 troops, including 200,000 to 250,000 cavalrymen.
[121] In order to sustain the military expeditions against the Xiongnu and its resulting conquests, Emperor Wu and his economic advisors undertook many economic and financial reforms, which proved to be highly successful.
[121]