|Demonstrations against Bahrain's government have been escalating since the Arab Spring [EPA]
In March, as a government crackdown on pro-democracy protestors intensified in Bahrain, curious advertisements started appearing in Pakistani media.
"Urgent requirement - manpower for Bahrain National Guard," said one.
"For service in Bahrain National Guard, the following categories of people with previous army and police experience are urgently needed," said another, with "previous experience" and "urgent need" underscored.
The categories included: former army drill instructors, anti-riot instructors, retired military police, and former army cooks.
In the following two months, on the back of visits to Islamabad by senior Saudi and Bahraini officials, sources say at least 2,500 former servicemen were recruited by Bahrainis and brought to Manama, increasing the size of their national guard and riot police by as much as 50 per cent.
"We know that continued airplanes are coming to Bahrain and bringing soldiers from Pakistan," Nabeel Rajab, president of the Bahrain Centre for Human Rights, told Al Jazeera.
"We do not know the exact number, but we know that it is much more than 1,500 or 2,000 people."
Recruited into the special forces, the national guard, and the riot police, the Pakistani citizens are tasked with suppressing Shia protesters that are reportedly demanding equal rights after years of alleged oppression at the hands of the royal family, part of Bahrain's Sunni minority.
"Our own Shia cannot join the security forces, but the government recruits from abroad," said Rajab.
On the ground in Pakistan, the recruitments were handled by the Fauji Foundation, one of the largest conglomerates in the country with close ties to the Pakistani military. In addition to the Overseas Employment Services, which is tasked with providing job opportunities for retired military personnel, the foundation owns large cereal and gas companies, sugar mills, security firms, as well as hospitals and universities.
|One of the adverts placed in Pakistani papers, reading: 'Urgent Need for Bahrain National Guard'
The Fauji Foundation did not respond to Al Jazeera's request for comment.
"Pakistanis, particularly Baluchs, make up a large part of the Bahraini force," said Fahad Desmukh, a former resident of Bahrain who now lives in Pakistan.
"They are extremely visible on the streets - so visible that the protestors were recently responding to the police in Urdu, knowing they did not speak Arabic." [Watch the video of protesters chanting 'police are crazy' in Urdu here.]
A small country of roughly 800,000 people (including about 235,000 non-nationals), Bahrain has a Defence Force of about 12,000 and a National Guard of 1,200, according to the US State Department.
The National Guard, which is in the foreront of the crackdown, seems to have been more than doubled by the recent recruitments of mostly Baluch servicemen.
"What it shows is that the Bahraini government has little trust in its own citizens to conduct security operations," Michael Stephens, a Qatar-based Bahrain specialist at the Royal United Services Institute, told Al Jazeera.
"So they rely on foreign recruits to unquestioningly carry out orders of violently suppressing protests."
While Arab nations have a long history of leaning on Pakistan for military expertise as well as foot soldiers, the recent increase in recruitments come at a tricky time. Pakistan has struggled to quell widespread ethnic violence and a robust insurgency on its own streets.
In the region, too, the country faces tremendous challenges.
"It has certainly put Pakistan in a very awkward position, where it has to balance its relationship with Iran on the one side and Saudi Arabia and Bahrain on the other," Stephens said.
Iran, a leading Shia country, has repeatedly denounced the Bahraini government's crackdown on the Shia - while Saudi Arabia has remained Bahrain's closest ally.
Inside Bahrain, the recruitments have brought dangers to the South Asian diaspora, where ill-feeling towards Pakistanis has increased, reportedly because they are seen as the main vehicle in the crackdown.
The influx of Sunni mercenaries has also increased fears that the government might be naturalising the new recruits in its efforts to change the country's Shia-majority demographic.
Video footage of Bahraini protesters chanting: 'Our police are Pakistani'. Al Jazeera cannot be held responsible for content hosted on third party sites [YouTube]
"In the 1970s and 80s, many Arab countries flushed with oil money bought state of the art equipment, but [the] local population lacked technical skills," said Hamid Hussain, a long time analyst and historian of the Pakistani military.
"A number of Pakistan army and air force personnel were deputed to several countries including Saudi Arabia, United Arab Emirates (UAE), Bahrain, Qatar, Jordan, Syria and Iraq. "
The recruitments varied from a dozen advisors to thousands of trainers and operators of complicated equipment.
The most prominent cases of such partnership was in 1970, when then Brigadier Zia ul Haq helped the Jordanian forces suppress Palestinians in what became known as "Black September".
Zia ul Haq, in one of the interesting paradoxes of the Pakistani military, later became a feared dictator who introduced a swift process of "Islamisation".
Pakistan's security relationship with Saudi Arabia, in particular, has put it at odds with Iran, its neighbour to the west. The two nations have been stuck in a Shia-Sunni rivalry for decades and have battled proxy wars across the region.
During the 1991 Gulf war, much to Saudi Arabia's apparent dismay, Pakistan turned down their request for preemptive help, in case Saddam Hussain launched attacks.
Reviving the relationship since has taken a long time, but when the uprising in Bahrain brought fears of unrest knocking on Saudi doors, the chairman of the Saudi National Security Council, Prince Bandar bin Sultan, made two quiet trips to Pakistan to seek their support in case protests erupted at home.
"Potential need for foreign troops in case protests spiral out of control has forced Saudis to work with current Pakistani civilian government for whom they have nothing but utter contempt," said Hussain.
Pakistani Prime Minister Yousuf Reza Gilani told Prince Bandar that his country supported the Saudi stance in the Gulf and the Middle East and would stand by Riyadh for regional peace, according to Pakistani media.
Al Jazeera's Fault Lines examines why the US supports protests in Libya - but not in Bahrain
"The president and prime minister of Pakistan, faced with grim economic situation of the country and army brass uncertain about continued US funding, are delighted at the potential of a cash windfall from Saudi patrons," said Hussain.
Also on Prince Bandar's agenda was gaining Pakistan's support for the Saudi-led Gulf Cooperation Council (GCC) force that deployed to Bahrain for helping the Kingdom.
The trip was followed by visits from the Bahraini foreign minister and the commander of their national guard.
Then, recruitment adverts appeared in Pakistani media.
Baluchistan, where most of the recruits come from, is a province of six million in Pakistan's southwest. For decades, an armed movement for self-determination there has been met with a severe government crackdown.
Baluch nationalist fighters expressed their dismay at the recruitment long before the recent escalation.
"We call upon the Baluch nation not to become part of any tyrant or oppressive army, at a time when the Baluch nation is living in a state of war … and are struggling against the tyrants ourselves," Basham Baluch, a spokesman for Baluch Liberation Front said in a 2009 statement.
"Instead of turning the young Baluch into hired killers, they should join the national armies [Baluch Liberation Front, Baluchistan Liberation Army] to make the independence of their homeland a reality.
"We do not want the Baluch people to be used and turned into mercenaries."
Bahrain is home to a large population of foreign labourers. The majority of the work forces there comprises South Asian migrants, particularly Pakistanis.
"Our country has a history of appreciation for the help Pakistanis have provided in development. But more recently we have seen crimes directed at Pakistanis, and that is worrying," said Rajab, the human rights activist.
He points to the fact that thousands of people have been arrested and hundreds of houses have been looted by government forces. Since Pakistanis make up at least 30 per cent of the security forces, he says, when people think of the crackdown they think of Pakistanis.
"The poor Pakistani labourer who has nothing do with security forces suffers from all this."
Human rights activists and analysts also fear that the government is swiftly increasing the rate of naturalisation for Sunni immigrants in recent months in order to tip the ethnic balance of the country.
With a clear Shia majority, the country has been ruled by a royal family from the Sunni minority.
"What needs to be closely watched is the number of these recruits who will be naturalised in the coming months and years ahead," said RUSI's Stephens.
"Many will not return home to Pakistan, and recent statistics show that South Asians make up a big majority of the foreign citizens naturalised in Bahrain."
While many believe Pakistan is providing workers and soldiers to Bahrain in return for much needed economic aid, activists such as Rajab remain perplexed by the decision.
"What I wonder is how the Pakistani government allows this many people to be brought here and used as mercenaries," said Rajab.
"We know that many of these recruits are poor, uneducated, and are just looking for a job. They don't know what they are signing up for. But the Pakistan government certainly knows, so why are they allowing this?"
Follow Mujib Mashal on Twitter: @mujmash