As claimed by The National Council of Resistance of Iran (NCRI), the Supreme Leader, Ali Khamenei, has spent billions in hardware for its ally Bashar al-Assad in the last five years.  “The Iranian HQ, which plays a pivotal role in supporting Assad’s regime alongside Russia, contains intelligence and counterintelligence operations, and has vaults packed with millions of dollars in cash flown in from Tehran,” according to the NCRI.

A dossier of reports was allegedly leaked by senior sources inside Iran’s Revolutionary Guards, which was then collated by the dissident activists.  The dossier, which could not be independently verified, is described as ‘credible’ by intelligence experts.The allegations contained in it claim that Iran controls the largest fighting force in Syria; has military bases throughout the state; and has amassed an enormous war-chest in support of the Syrian president.

According to Simmons, “If the activists’ claims are accurate, this would mean that the fundamentalist Tehran regime and its Shia proxies are far more powerful than has been estimated. Western analysts have so far placed the total Iranian-led Shia force at just 16,000.  The dissidents make the claim that Iran now commands about 60,000 Shia troops in Syria – 15,000 more men than Britain took into the 2003 Iraq war – while Assad’s army has been reduced to just 50,000 soldiers.”

The intelligence that the NCRI passed to MailOnline claims that a staggering $100 billion has been spent by Iran to assist in the conflict since 2011, in support for Assad’s regime. This  figure surprised Western analysts, whose estimates have been far less.

“Millions of dollars in cash is regularly delivered at the Iranian airstrip before being transferred to the HQ nicknamed ‘the Glasshouse’,” the dissidents claim.  The money is allegedly stored in the basement under the care of, Brigadier General Seyyed Razi Mousavi, formerly commander of the elite Quds Force in Syria. It is principally used to pay fighters’ salaries.

The NCRI is the Iranian opposition group committed to the overthrow of the Rouhani regime. It has leaked intelligence in the past, exposing the existence of secret nuclear facilities at Natanz and Arak, which made Western powers more cautious in negotiating with Tehran.

Kamal Alam, a research analyst at the Royal United Services Institute (RUSI), said that the leaked intelligence was, ”…entirely plausible’. I go quite regularly to Syria and visit the battlefields, and I’ve seen how the Iranians try to keep their operations as secret as possible. Their troops tend to speak Arabic rather than Farsi in public, and generally don’t wear Iranian uniforms. This makes it very hard for observers to know how many are in the country.” He added that analysts have been forced to use conservative estimates of troop numbers, because Tehran does not release reliable figures.  Syria’s President Assad, downplays Iran’s support to avoid the impression that he is a puppet of the Islamist regime, according to Alam.

The activists’ key claim is that Iran operates a major HQ close to Damascus airport, which the NCRI say is nicknamed The Glasshouse (Maqar-e Shishe’i in Farsi).  The NCRI say that the 180-room building is nicknamed ‘Muhammad Ali’, and that anti-blast walls form a square around the perimeter, which is heavily guarded. According to the NCRI, up to 1,000 personnel work at the secret base, and all must undergo an intensive security screening.  A number of departments are based inside including the feared Iranian intelligence services, who are in charge of the base.

Simons says, “The revelations come after Tehran took the extraordinary step of allowing Russia to use its airbases to launch attacks in Syria, demonstrating its expanding role.

It also follows reports that Iran has deployed a Russian-made S-300 surface-to-air missile defense system at its uranium enrichment facility at Fordow, northwestern Iran.”

Dr Aniseh Bassiri Tabrizi, an Iran specialist at RUSI, said: ‘It is very difficult to know about numbers because Iran is so secretive. It’s something we struggled with throughout our research.  It’s no secret that Iran has a heavy presence on the ground that is not based exclusively on advisers and consultants. This data reinforces our assumptions and suspicions about Iranian involvement in Syria, but takes it much further in terms of numbers.  It amplifies our view that because of the heavy political, financial and military investment in Syria, Iran is unlikely to withdraw its presence on the ground without a major shift in the power balance.” 

Iran’s role in fostering instability in the Middle East, including ongoing support for proxy groups and the Assad regime, and the activities of the Quds force, remains a source of serious concern,” a Foreign Office spokeswoman told MailOnline.

The NCRI also claim Tehran has military in 18 locations from northern to southern Syria, pointing out that it it intends to control large swathes of the country even if Assad is defeated.

One security source told MailOnline, “Iran is getting itself into a position where whether Assad stands or falls, Tehran is in the best position to dominate whatever comes next.’

Such is the scale of Tehran’s involvement in Syria that the war has been taking its toll domestically, the dossier claims. Last year, just 5,000 Iranians were in action in the country; today, this number stands at 16,000. “

According to Rusi’s Iran specialist Dr Tabrizi, the massive Iranian presence raises the danger of regional escalation. “The Gulf countries are already scared about Iranian power projection in the region. This may hasten [the Gulf states’] support for rebel groups, or even lead them to think about the deployment of ground troops to Syria,” Dr. Tabrizi said. 

According to activists, the role of Iran goes even further, who also claim that the state encouraged Russia to commit significant resources to bolster Assad in 2015.

“During a secret meeting with Moscow in July last year,  Major General Qasem Soleimani apparently requested greater Russian air support and a huge shipment of weapons, including MiG, Sukhoi and Antonov aircraft, Kamov and Mil helicopters, and T90 tanks,” according to Simons.  Dissidents citing Revolutionary Guards sources claim that a deal was done on condition that Iran paid $3 billion towards the $10 billion cost.

“You’re talking about a very orchestrated, emboldened and well-planned Iranian presence,” one security source told MailOnline. “They are thinking very clearly and wisely, and are putting down deep roots, creating pockets of power in places with strategic importance.  The Iranians are masters in meddling in different political functions abroad. It is exactly what many in the region are afraid of. It’s their biggest nightmare.”

A Foreign Office spokeswoman said, “The Iranian government has said that it wants to see a peaceful solution to the Syrian conflict. But as thing stand, Iran is a long way from playing a constructive role. Iran continues to send fighters, including the Revolutionary Guards Quds Force, to Syria, subsidises the Assad regime and is actively supporting the Assad regime’s suppression of innocent people.”