Though Chinese potters developed underglaze red decoration during the Yuan dynasty (AD 1279-1368), pottery decorated in underglaze blue was produced in far greater quantities, due to the high demand from Asia and the Islamic countries of the Near and Middle East. Painting with underglaze red was more difficult than underglaze blue: the copper oxide used as the colouring agent was harder to control than the cobalt that was used for the underglaze blue. The firing left parts of the red areas grey, as on this large jar.The first emperor of the Ming dynasty, which was to rule China for the next 300 years, was the general Zhu Yuanzhang (reigned 1368-98), whose title was Hongwu. He overthrew the Yuan dynasty, whose rulers had been foreigners (Mongols). He was determined to re-establish the dominance of Chinese style at court, and blue-and-white porcelain was produced in designs following Chinese rather than Islamic taste. Similar pieces were executed with underglaze red for use by the emperor.Hongwu banned foreign trade several times, though this was never fully effective. The import of cobalt was disrupted, however, which resulted in a drop in the production of blue-and-white porcelain. For a short time at the end of the fourteenth century, more wares were decorated with underglaze red than underglaze blue.