Among the many mysteries inside Iran's ruling hierarchy, the Quds Force has a special place in the shadows. It's been linked by Western officials and others to dozens of clandestine operations around the world such as a deadly bombing of a Jewish cultural center in Buenos Aires in 1994, aiding Shiite militias in Iraq and helping arm Afghanistan's Taliban — and now as the alleged masterminds of a plot to kill the Saudi Arabian ambassador in Washington. The Quds Force — with between 5,000 and 15,000 agents and field tacticians by various estimates — sits atop the vast military and industrial network of the Revolutionary Guard, the defenders of Iran's ruling clerics and their hold on power. The Guard effectively has a blank check. It controls most major programs — including nuclear, missile development and Iran's budding space efforts — as well as a millions-strong paramilitary corps known as the Basiji that's been used as street muscle to put down protests. The Quds Force is seen as the Guard's A-team around the world. The favored route, experts say, is the low-risk channels of arming and training proxies. In July, the US military's top spokesman in Iraq, Maj. Gen. Jeffrey S. Buchanan, attributed a sharp rise in attacks to a suspected Quds-aided faction known as the Hezbollah Brigades. Earlier this year, Western intelligence officials in Afghanistan claimed a Taliban leader met in Iran with Quds Force personnel to ask for stronger weapons to fight NATO forces. A 2007 report by the Washington-based Center for Strategic and International Studies claimed that Quds agents have special “sections” in Iranian embassies that are off limits to regular diplomatic staff. It's unclear, the report said, whether even the ambassadors have full knowledge of Quds Force operations. “Its ranks are said to be comprised of Iran's most highly skilled special operations and intelligence officers,” said Michael S. Smith II, a counterterrorism expert and co-founder of the security consultant group Kronos Advisory, which presented a report on the Quds Force to a congressional caucus in April. The report described the Quds Force as part of a “known unknown” for Western security officials trying to track its network. In August, the European Union announced imposed harsher sanctions against the Quds Force, saying it had given support to Syrian President Bashar Al-Assad – a key Iranian ally – in attacks against anti-government protesters. The US Treasury in 2007 declared the Quds Force a “specially designated global terrorist organization.” Iran, however, barely acknowledges the Quds Force exists. The group is not mentioned in the national budget and doesn't openly participate in military parades alongside its Revolutionary Guard partners. A former CIA officer, Robert Baer, has said it's believed that the Quds Force requires the use of couriers for all sensitive communications — a technique that was also used by Osama Bin Laden. One of the few public faces with known Quds links is Defense Minister Gen. Ahmad Vahidi, who was the force's commander during the 1994 bombing of a Jewish cultural center in Buenos Aires that killed 85 people. Vahidi and four others are wanted by Argentina in connection with the attack. Quds commanders, however, come under no public scrutiny in Iran and have an open door to Supreme Leader Ayatollah Ali Khamenei, who has the last word in all major affairs.