Although Qatar was considered a dependency of Bahrain, the Al Khalifa faced opposition from the local tribes. In 1867, the Al Khalifa, along with the ruler of Abu Dhabi, sent a massive naval force to Al Wakrah in an effort to crush the Qatari rebels. This resulted in the maritime Qatari–Bahraini War of 1867–1868, in which Bahraini and Abu Dhabi forces sacked and looted Doha and Al Wakrah. The Bahraini hostilities were in violation of the Perpetual Truce of Peace and Friendship of 1861. The joint incursion, in addition to the Qatari counter-attack, prompted British Political Resident, Colonel Lewis Pelly to impose a settlement in 1868. His mission to Bahrain and Qatar and the resulting peace treaty were milestones because they implicitly recognised the distinctness of Qatar from Bahrain and explicitly acknowledged the position of Mohammed bin Thani. In addition to censuring Bahrain for its breach of agreement, Pelly negotiated with Qatari sheikhs, who were represented by Mohammed bin Thani. The negotiations were the first stage in the development of Qatar as a sheikhdom. However, Qatar was not officially recognised as a British protectorate until 1916.