The Silk Road trade, which involved mostly prestige goods, started from the Han dynasty, around the second century bce, under the protection of Han imperial expansion into Central Asia. The economy of the Han Empire was mainly based on agriculture. Taxes in the form of agricultural products – such as food grains, silk yarn and floss, and bast-weave cloths such as ramie and hemp – in addition to corvée labor provided the major revenue for the state. Although commerce flourished in cities and connected both rural and urban residents into a nationwide market, traders held the lowest status in the social hierarchy. The impetus for trade with foreign countries, therefore, was initiated by the Han ruling elite, who, like aristocrats in ancient regimes around the world, had always been looking for rare and expensive goods to mark their distinguished status. Meanwhile, the Han Empire engaged in warfare with pastoral nomads of the Central Asian steppe grasslands from the founding of the dynasty. The perennial wars with the Xiongnu nomad confederation extended the horizon of the Han rulers, north to the steppe and west to Central and South Asia, reaching as far as the Mediterranean.