The economic power of Song China heavily influenced foreign economies abroad. The Moroccan geographer al-Idrisi wrote in 1154 of the prowess of Chinese merchant ships in the Indian Ocean and of their annual voyages that brought iron, swords, silk, velvet, porcelain, and various textiles to places such as Aden (Yemen), the Indus River, and the Euphrates in modern-day Iraq. Foreigners, in turn, affected the Chinese economy. For example, many West Asian and Central Asian Muslims went to China to trade, becoming a preeminent force in the import and export industry, while some were even appointed as officers supervising economic affairs. Sea trade with the South-west Pacific, the Hindu world, the Islamic world, and East Africa brought merchants great fortune and spurred an enormous growth in the shipbuilding industry of Song-era Fujian province. However, there was risk involved in such long overseas ventures. In order to reduce the risk of losing money on maritime trade missions abroad, wrote historians Ebrey, Walthall, and Palais: