Under the Anglo-Dutch Treaty of 1824 the British ceded their colonial possessions on Sumatra to the Dutch. In the treaty, the British described Aceh as one of their possessions, although they had no actual control over the Sultanate. Initially, under the agreement the Dutch agreed to respect Aceh's independence. In 1871, however, the British dropped previous opposition to a Dutch invasion of Aceh, possibly to prevent France or the United States from gaining a foothold in the region. Although neither the Dutch nor the British knew the specifics, there had been rumors since the 1850s that Aceh had been in communication with the rulers of France and of the Ottoman Empire.