ABU DHABI // The UAE forces that entered Bahrain this week are part of a pan-Gulf military force that has rarely been called into action.
The Peninsula Shield Force, officially created in 1982, took part in the liberation of Kuwait during the First Gulf War in the early 1990s, and was again sent to Kuwait in 2003 ahead of the US-led invasion that toppled Saddam Hussein.
Now its forces are in Bahrain to help restore order amid ongoing unrest.
Its formation and development run in parallel with growing military and security co-operation between the six states of the Gulf Co-operation Council — the UAE, Saudi Arabia, Bahrain, Oman, Kuwait and Qatar.
The GCC defines two phases of the development of military ties among its member states.
The first phase set the foundations for this military partnership, and its crowning achievement was the creation of the Peninsula Shield Force (PSF) in November 1982 at the third summit of the GCC's Supreme Council, comprised of the rulers of the Gulf states.
That pact established the PSF and its overarching mission, with its first training exercise was held in October 1983 in the UAE, though the force was not fully formed until 1985.
It was based in north-eastern Saudi Arabia, in the city of Hafr al Batin, close to both the Kuwaiti and Iraqi borders.
The PSF's formation heralded closer military ties, with joint planning sessions and training exercises for the Gulf's militaries. The size of the force was estimated at a modest 5,000 soldiers at its inception, but has since grown six-fold.
The second phase saw the cementing of the joint defence responsibilities of the member states, with the signing of a mutual defence pact at the 21st GCC summit in Manama on December 31, 2000.
The treaty - which also created a joint GCC defence council and a high military committee - codified what is now the pillar of the GCC's military doctrine: that the security of all the members of the council is an "indivisible whole".
That joint security strategy was first formulated at a meeting of the Gulf's interior ministers in 1982.
"The security of the council's states is an indivisible whole, and any aggression on a member state is aggression against the other states, and facing aggression is considered a joint responsibility whose burden is on all the member states," the ministers declared in their communique.
"Interference from any entity in the internal affairs of one of the member states is interference in the internal affairs of all the nations of the council."
The communique thus made attacks by a foreign force, foreign interference and destabilisation of a GCC state all contingencies that demand unified action by the council.
In 1990, the GCC began modernising the PSF, turning it into a mechanised infantry division with support units. Some published reports say the force now includes air and naval capabilities.
A proposal by Saudi Arabia's King Abdullah, adopted in 2006 by the Gulf Supreme Council, transformed the PSF.
It was agreed that soldiers would be stationed in their home countries but come under joint command. The process is for a Gulf state to ask for the assistance of the PSF, as Bahrain has done.
Projects linking the communication networks of the GCC's militaries through fibre optic cables, as well the operations centres of the states' air forces, were completed in the summer of 2000.
While several Gulf states hold annual joint military exercises, the Peninsula Shield Force holds training exercises every two years with one of the Gulf's militaries.
The UAE was the first country to arrive in Kuwait in 2003 as part of the Peninsula Shield contingent.
At the most recent GCC summit in Abu Dhabi in December Sheikh Abdullah bin Zayed, the UAE's Minister of Foreign Affairs, when asked about the size of the Peninsula Shield forces, and whether they were large enough, spoke of the necessity of maintaining and improving the Gulf's militaries.
Sheikh Abdullah reiterated the Gulf's support for a common defence strategy.
"After the tragedy of Saddam Hussein's invasion of Kuwait, there was a big improvement in the system, methods, training of the armed forces in the Gulf," he said.
Sheikh Abdullah confirmed that the PSF consisted now of 30,000 troops, but said that close military ties always bound the states of the GCC.
"There are no barriers between the armed forces in the UAE and the ones in Kuwait," he said. "Any attack on one of the council's states is an attack on the entire council."
Still, military officials have often called for more joint GCC defence work, such as co-ordinated missile defence systems and navies.
The UAE has set itself up as a vital military training centre that is open to other Gulf states.
Today, some Arab and Gulf fighter pilots are taking part in training exercises at the Air Warfare Centre in Al Dhafrah Air Base, and the UAE is setting up a missile defence simulation centre in Al Bateen Air Base in co-operation with the US.
In the past three years, the UAE has hosted joint military training exercises with Qatar, Bahrain and Kuwait in addition to joint sessions with security forces from Oman and Saudi Arabia.
Co-operation has also extended to internal security, with the creation of a Gulf committee that meets annually to debate counter-terrorism policies.
GCC states are also working on a joint plan to deal with potential radiation or nuclear fallout, and have developed joint, model legislation on punishing crimes involving narcotics.