The UAE was formed from the group of tribally-organized Arabian
Peninsula shaikhdoms along the southern coast of the Persian Gulf and
the northwestern coast of the Gulf of Oman. This area was converted to
Islam in the 7th century; for centuries it was embroiled in dynastic
disputes. It became known as the Pirate Coast as raiders based there
harassed foreign shipping, although both European and Arab navies
patrolled the area from the 17th century into the 19th century. Early
British expeditions to protect the India trade from raiders at Ras al-
Khaimah led to campaigns against that headquarters and other harbors
along the coast in 1819. The next year, a general peace treaty was
signed to which all the principal shaikhs of the coast adhered. Raids
continued intermittently until 1835, when the shaikhs agreed not to
engage in hostilities at sea. In 1853, they signed a treaty with the
United Kingdom, under which the shaikhs (the "Trucial Shaikhdoms")
agreed to a "perpetual maritime truce." It was enforced by the United
Kingdom, and disputes among shaikhs were referred to the British for
settlement.

Primarily in reaction to the ambitions of other European countries, the
United Kingdom and the Trucial Shaikhdoms established closer bonds in an
1892 treaty, similar to treaties entered into by the UK with other Gulf
principalities. The shaikhs agreed not to dispose of any territory
except to the United Kingdom and not to enter into relationships with
any foreign government other than the United Kingdom without its
consent. In return, the British promised to protect the Trucial Coast
from all aggression by sea and to help out in case of land attack.

In 1955, the United Kingdom sided with Abu Dhabi in the latter's dispute
with Saudi Arabia over the Buraimi Oasis and other territory to the
south. A 1974 agreement between Abu Dhabi and Saudi Arabia would have
settled the Abu Dhabi-Saudi border dispute; however, the agreement has
yet to be ratified by the UAE Government and apparently is not
recognized by the Saudi Government. The border with Oman also remains
unsettled.

In 1968, the UK announced its decision, reaffirmed in March 1971, to end
the treaty relationships with the seven Trucial Shaikhdoms which had
been, together with Bahrain and Qatar, under British protection. The
nine attempted to form a union of Arab emirates, but by mid-1971 they
were unable to agree on terms of union, even though the termination date
of the British treaty relationship was the end of 1971. Bahrain became
independent in August and Qatar in September 1971. When the British-
Trucial Shaikhdoms treaty expired on December 1, 1971, they became fully
independent. On December 2, 1971, six of them entered into a union
called the United Arab Emirates. The seventh, Ras al-Khaimah, joined in
early 1972.

source: U.S. State Department Background Notes 1991