The Islamic Revolutionary Guard Corps (IRGC) is Iran's elite military force responsible for protecting the Islamic regime from internal and external threats. 

A 125,000-man force, it also controls the paramilitary Basij militia, which has about 90,000 active members, and runs the foreign special operations Quds force.  

The IRGC was established at the end of Iran's 1979 Islamic Revolution as an elite armed militia whose role was to protect the then embryonic Shiite clerical regime. It also formed an important counterweight to Iran's conventional military, many of whose leaders were believed to be loyal to the exiled shah.

The IRGC initially operated as a domestic force, but expanded quickly after Iraqi dictator Saddam Hussein invaded Iran in 1980, when Ayatollah Ruhollah Khomeini gave the group its own ground, naval and air forces.

IRGC hands are everywhere

Some analysts have argued the IRGC has since become a state-within-a-state, a visible manifestation of what is usually referred to as the "deep state" in other — less authoritarian — countries.  

The IRGC's role is enshrined in the constitution and it answers only to Iran's supreme leader, Ayatollah Ali Khamenei, thus also endowing it with an enormous range of legal, political and in effect also religious powers. 

Read more: 'The Revolutionary Guards are Iran's true rulers'

The group oversees Iran's ballistic missile program and has conducted several tests since the nuclear deal. Its missiles can reach Israel and in March 2016 it launched a ballistic missile with the words "Israel must be wiped out" in Hebrew.

The IRGC's power base reaches into the furthest corners of the Iranian state, a network that effectively runs the military and intelligence complexes. 

Iran's president, the reformist Hassan Rouhani, has had an up-and-down relationship with the IRGC. He has sought to reduce the IRGC's influence over the economy as part of economic reforms. 

It is reported to have a large stake in the Iranian economy, both in legal and illegal entities, with commanders also owning real estate in Tehran. The group is also often accused of engaging in lucrative cross-border smuggling.

Its intelligence network has been behind the arrests and convictions of dual nationals and those with Western ties on espionage charges in closed hearings.

Quds hold the keys

Khamenei, who succeeded Khomeini in 1989, created the Quds force, a unit of the Revolutionary Guard in charge of its overseas operations.

Sometimes known as the successor to the shah's Imperial Guards, the Quds are estimated to be 2,000-5,000 in number.

Headed by Major General Qassem Soleimani, who has advised forces fighting the "Islamic State" in Iraq and Syria on behalf of Syrian President Bashar Assad, the Quds works with Hezbollah in Lebanon and Hamas in Gaza, two organizations the government openly parades as allies.

A terrorist group?

The United States has accused Iran of being a state sponsor of terrorism, but has refrained from listing the IRGC as a terror group over concern that move could lead to attacks on US forces in the region. It would also be unprecedented for a country's military to be labeled a terrorist group. 

However, the US maintains sanctions on Iran and the IRGC over the supporting of terrorism, mainly due to their military support for Hezbollah and Hamas.