The Yuan dynasty and the expanding Sino-Arab trade during the 14th century had gradually expanded Chinese knowledge of the world since universal maps previously displaying only China and its surrounding seas began to expand farther and farther southwest, with much more accurate depictions of the extent of Arabia and Africa. Between 1405 and 1433, the Ming government sponsored seven naval expeditions. The Yongle Emperor, disregarding the Hongwu Emperor's expressed wishes, designed them to establish a Chinese presence and impose imperial control over the Indian Ocean trade, impress foreign peoples in the Indian Ocean basin, and extend the empire's tributary system. It has also been inferred from passages in the History of Ming that the initial voyages were launched as part of the emperor's attempt to capture his escaped predecessor, which would have made the first voyage the largest-scale manhunt on water in the history of China.