Key Point: Despite sanctions, Iran's military has improved its capabilities over the years.

With the possible exception of North Korea, no country in the post–Cold War era has sought to challenge the United States as much as Iran. From the Middle East to Central Asia to Latin America, Tehran has never missed an opportunity to antagonize the U.S. and limit its influence.

This is an inherently risky strategy. Not only has the U.S. encircled Iran with military bases on all sides, but America’s military spending in recent years has been twice the size of Iran’s entire GDP. In any conventional military conflict, Iran wouldn’t stand a chance against the U.S. armed forces.

To compensate, Iran pursues a deterrent-based military doctrine premised on three types of capabilities: an expansive ballistic missile arsenal, asymmetric naval warfare (particularly the threat of closing down the Strait of Hormuz), and ties to non-state militant groups. Although many weapon systems go into implementing this doctrine, five capabilities are particularly crucial:

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Sejjil Missile

The most blunt instrument in Iran’s military doctrine is its large inventory of ballistic missiles. Of these, the Shahab family of ballistic missiles, which are based on North Korean designs, are the best known.

The Sejjil-1 (and its successor, the Sejjil-2) should be the most feared, however. The Sejjil-1 is a two-stage, medium range surface-to-surface ballistic missile that Iran first tested in 2008. Unlike the Shahab missiles, the Sejjil-1 missile is solid-fueled, greatly reducing its launch time while enhancing its mobility.

In Congressional testimony in November 2009, then U.S. Defense Secretary Robert Gates said that the “The [Sejjil] missile will have a range of approximately 2,000 to 2,500 kilometers.” This is consistent with the ranges given by Iranian officials like Defense Minister Brigadier General Mustafa Mohammad. At this range, the Sejjil-1 can deliver a 750 kg payload to Israel and even parts of southeastern Europe. It is widely believed that this could someday be a nuclear payload.

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The Sejjil-2 was first tested in 2009 and is likely still under development. According to Global Security, “The Sejjil-2 has an demonstrated range capability of 2,510 kilometers with its 650 kilogram tri-conic warhead re-entry vehicle design. It can also carry a 1,000 kilogram warhead to 2,000 kilometers.” The Sejjil-2’s biggest advancement is in accuracy, something Iranian ballistic missiles have traditionally lacked. Iranian defense officials have said that compared with the Sejjil-1, the Sejjil-2 is “equipped with a new navigation system as well as precise and sophisticated sensors.”

Ghadir-class midget submarines

Perhaps Iran’s greatest deterrent threat is its ability to threaten oil shipments in the Strait of Hormuz, which roughly 20 percent of global oil supplies must transverse on their way to markets. Indeed, according to some estimates, the U.S. has spent some $8 trillion protecting the Strait of the Hormuz since 1976.

Submarines would be invaluable for Iran were it to try and close the Strait of Hormuz. As the Institute for the Study of War (ISW) has explained, “In the confined and shallow waters of the Arabian Gulf, the ability to deploy submarines effectively threatens surface vessels that are channeled into narrow Sea Lines of Communication.” These narrow SLOCs force military and commercial ships to travel predictable routes, making them easy prey for submarines.

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Iran has a number of different types of submarines, but its growing fleet of 150-ton Ghadir-class (Qadir/Khadir) midget submarines would be especially deadly in any conflict. A variant of the North Korean Yugo and Sango-class submarines, the small size and acoustic signature of the Ghadir-class make them especially hard to detect and track. Each sub packs two 533-mm tubes for firing torpedoes, is capable of laying mines and, according to Iranian media outlets, could be used to transport and insert special forces into enemy territory.

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The subs are not of particularly high quality, but, as is often the case with Iranian naval capabilities, quantity matters. Iran has at least twenty Ghadir-class subs compared to less than a handful of its other types of submarines. These numbers are crucial for how Iran would use the Ghadir-class subs in any conflict. As Chris Harmer, an expert on Iran’s military at the ISW, explained to me in 2013, “The quietest submarine in the world is one that rests on a sandy seabed. That is how the Iranians would use the Ghadir—get it out of port, sink to the bottom of the shallow Persian Gulf, rest on the sandy bottom, and wait for a target to come to it.”

Khalij-e Fars Missile

The Khalij-e Fars anti-ship ballistic missile (ASBM) is another valuable component of Iran’s asymmetric naval capabilities.

Often called Iran’s “carrier-killer,” the Khalij-e Fars (Persian Gulf) is a is a solid-fuel, supersonic Anti-Ship Ballistic Missile (ASBM) with a range of 300 km when carrying a 650-kg payload. It is based on the Fateh-110, a single-stage solid-propellant, surface-to-surface missile that Iran first tested in 2002 (The Fateh-100 is based off of the China-made DF-11A).

Iranian media outlets have described the Khalij-e Fars as the “most advanced and most important missile of the IRGC Navy” and said, “the distinctive feature of the missile lies in its supersonic speed and trajectory. While other missiles mostly traverse at subsonic speeds and in cruise style, the Persian Gulf moves vertically after launch, traverses at supersonic speeds, finds the target through a smart program, locks on the target and hit it.”

The Khalij-e Fars was first tested in 2011 and has been tested regularly ever since. Iran claimed that the second test of the ASBM in July 2012 hit a moving vessel with a 30-meter precision rate. The following year, Brigadier General Amir-Ali Hajizadeh, Commander of the Islamic Revolutionary Guards Corps’ (IRGC) Aerospace Division, claimed that Iran had increased the missile’s precision from 30 meters to 8.5 meters.

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Many foreign experts have been skeptical of these claims. Chris Harmer, the Iran military expert at ISW, told me at the time of Hajizadeh’s announcement that “We do not know, in open source, the exact performance specifications of Iranian missiles. This applies equally to ballistic missiles, cruise missiles, and anti-ship missiles, of both the ballistic and cruise missile varieties.”

Iran’s intentions with its “carrier-killer” are more transparent; Fars News Agency, which is close to the IRGC, bluntly stated the missile is “designed to destroy targets and hostile forces at sea.” Deputy Defense Minister General Majid Bokayee similarly boasted that “we witnessed the US naval fleets' retreat in the Persian Gulf after the first test on the missile.”

Hezbollah

At the time, the decision to send IRGC officials to Lebanon in the early 1980s to help foment resistance to Israel’s occupation reeked of revolutionary fanaticism. Not only had Iran not traditionally exercised influence in Lebanon, but it was locked in a life and death struggle with Saddam Hussein’s Iraq. Domestically, the country was also still reeling from the aftermath of the 1979 revolution.

With the benefit of hindsight, the decision to infiltrate Lebanon seems like pure strategic genius, as Hezbollah has been the gift that just keeps giving for Iran. Time and again Hezbollah has proven to be the most versatile and usable “weapon of war” in Iran’s arsenal. And it isn’t even close.

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Oftentimes, Iran has used Hezbollah to carry out traditional terrorist attacks like the 1994 bombing of a Jewish community center in Buenos Aires, Argentina, which killed eighty-five people and injured scores of others. Indeed, Hezbollah’s greatest value to Iran may be its operational reach. Whereas Tehran’s Qud Forces have often struggled to execute attacks outside of the Middle East, Hezbollah has shown no such limitations. For example, in early 2012, Iranian operatives working for the Qud Forces tried to attack Israeli targets in places like India, Georgia, Thailand and Kenya in retaliation for Israel’s suspected assassinations of Iranian scientists. In each case, the Iranian operatives botched the attacks, sometimes embarrassing themselves in the process (Iran’s alleged attempt to assassinate the Saudi Ambassador to the United States was also a comical failure.) Following the Quds Forces’ botched attempts, Iran turned to Hezbollah, which successfully attacked Israeli tourists in Bulgaria.

Hezbollah’s utility to Iran has increasingly gone beyond traditional terrorist attacks. Following the U.S. invasion of Iraq in 2003, Iran used Hezbollah to train Iraqi Shi’a militant groups. There have also been reports that Hezbollah militants have helped train Houthi rebels in Yemen, who have overrun most of the capital city of Sanaa in recent weeks. Most notably, Hezbollah has been indispensable in propping up the Bashar al-Assad regime in Syria since 2011.

Zachary Keck is the former managing editor of the National Interest. This first appeared several years ago and is being republished due to reader interest.