The British government concluded "protection and friendship" treaties with nine tribes surrounding Aden, whereas they would remain independent from British interference in their affairs as long as they do not conclude treaties with foreigners (non-Arab colonial powers). Aden was declared a free zone in 1850. With emigrants from India, East Africa, and Southeast Asia, Aden grew into a world city. In 1850, only 980 Arabs were registered as original inhabitants of the city. The English presence in Aden put them at odds with the Ottomans. The Turks asserted to the British that they held sovereignty over the whole of Arabia, including Yemen as the successor of Mohammed and the Chief of the Universal Caliphate.