in good health above 20, was eligible for two years of military service or one month of military service and one year of corvee labour (later those above 56 were exempt from any military or corvee labour service). Emperor Wu, on the other hand, sparked debate when he intervened into the economy to pay for his wars. His interventions were hotly debated between the Reformists, who were composed mainly of Confucian scholars favoring laissez-faire policies, and the Modernists, a group of government officials who supported the state monopolies on salt and iron and high taxation policies that Emperor Wu had pioneered. These debates were recorded in the book Discourses on Salt and Iron, an important document showing ancient Chinese economic thought. Although the Modernist policies were followed through most of the Western Han after Emperor Wu, the Reformists repealed these policies in Eastern Han, save for the government monopoly on minting coins. Han industry In the early Western Han, the wealthiest men in the empire were merchants who produced and distributed salt and iron and gained wealth that rivalled the annual tax revenues collected by the imperial court. These merchants invested in land, becoming great landowners and employing large numbers of peasants. A salt or iron industrialist could employ over one thousand peasants to extract either liquid brine, sea salt, rock salt, or iron ore. Advanced drilling techniques that allowed drilling up to 4800 feet/1440 metres were developed, allowing Chinese to extract salt and even natural gas for use in fuel and lighting. Emperor Wu of Han (r. 141–87 BCE) viewed such large-scale private industries as a threat to the state, as they drew the peasants' loyalties away from farming and towards the industrialists. Nationalising the salt and iron trades eliminated this threat and produced large profits for the state. This policy was in line with Emperor Wu's expansionary goals of challenging the nomadic Xiongnu Confederation while colonising the Hexi Corridor and what is now Xinjiang of Central Asia, Northern Vietnam, Yunnan, and North Korea. Historian Donald Wagner estimates that the production of the Han iron monopoly was roughly around 5,000 tons (assuming 100 tons per iron office). Although many industrialists were bankrupted by this action, the government drafted former merchants like Sang Hongyang (d. 80 BCE) to administer the national monopolies. Although a political faction in the court succeeded in having the central government monopolies abolished from 44 to