In the late 1950s Mao embarked on one of his most ambitious programs, the Great Leap Forward (GLF). The GLF stressed an approach, as Mao said, of "walking on two legs," that is the simultaneous development of both agriculture and industry. Nearly 100 million people smelted steel at some 600,000 small blast furnaces like the one pictured here. The problem was that this distracted peasants from agricultural work. Also, much of the steel produced was of poor quality and could not be used. The GLF had a lasting ecological impact because trees were cut down to fuel the furnaces, leading to heavy deforestation. Finally, unfortunately for Mao the GLF coincided with a series of natural disasters in 1960 that, combined with the drop in agricultural production due to the campaign, led to what is widely believed to be the worst famine in human history, costing an estimated 20 million deaths. Source: Instructional Resources Corporation, The World History CD-Rom (non-European history).