This paper characterizes the pursuit of sustainability as a three-front war. Success requires reductions not only in the environmental impact per unit of economic activity, but also in the economic growth to which we have become accustomed and the inequality that has accompanied it. To explain the difficulty in responding to this threefold challenge, the paper reviews historical data on the evolution of the global economy. Based on this review the paper argues that the explosive growth experienced since 1950 has created a world in which rapid progress toward and beyond affluence is ‘business as usual.’ The pursuit of sustainability is difficult in large part because it takes place within this world shaped by explosive growth. An income transition is suggested as part of the effort to fight the three-front war.