Iran's Revolutionary Guards commander Mohammad Ali Jafari looks on while attending Friday prayers in Tehran February 10, 2012. REUTERS/Morteza Nikoubazl On April 27, the head of Iran's Islamic Revolutionary Guard Corps (IRGC), Maj. Gen., Mohammad Ali Jafari lashed out at Saudi Arabia and its recent military intervention in Yemen, accusing the "treacherous Saudis" of "following in Israel's footsteps" by "shamelessly and disgracefully bombing and mass killing" the Yemeni people.

The increased Saudi aggression in the region, he contended, demands a tougher response from Tehran.

Similarly, Hezbollah deputy secretary-general Naim Qassem warned in an April 13 interview with the Associated Press that the kingdom will "incur very serious losses" and "pay a heavy price" as a result of its Yemen campaign.

Given historical precedent — not to mention numerous other angry statements from Tehran of late (see PolicyWatch 2423, "Yemen's War Heats Up Iran's Anti-Saudi Rhetoric") — Riyadh should take such threats at face value.

Targeting Saudi interests

Iran has a long history of plotting attacks against its Saudi rivals in response to transgressions real and perceived.

These plots, carried out by Iranian agents and Hezbollah proxies, have targeted Saudi interests in the Middle East and elsewhere. One of the most recent — traced back to IRGC Qods Force commander Qasem Soleimani and other senior Iranian decisionmakers — was the failed October 2011 plot to assassinate the Saudi ambassador in Washington by bombing a restaurant he frequented.

Yet Tehran's earliest anti-Saudi schemes stretch back nearly to the regime's founding.

Just three months after its creation in May 1987, the Saudi branch of Hezbollah (a.k.a. Hezbollah al-Hejaz) carried out its first attack inside the kingdom. Previously, a confrontation between Shiite pilgrims and Saudi security forces at the July 1987 Hajj turned violent, escalating into a stampede that killed more than 400 people. Among the dead were a number of Saudi policemen and Iranian pilgrims, and rumors spread that some of those killed were tied to Saudi Shiite political and militant organizations.

Seeking retaliation, Iran began courting radical Shiites in the kingdom's Eastern Province to carry out attacks. A week after the tragedy, Saudi Hezbollah issued its first official statement, vowing to challenge the ruling family.

The following month, it claimed responsibility for an attack against a petroleum facility in Ras al-Juaymah. In communiques issued in Beirut and Tehran, the group threatened to carry out additional revenge attacks targeting Saudi officials. And a month later, it threatened attacks against US and Saudi interests abroad.

Rescue and clean-up crews search for casualties following the US Marine barracks bombing in Beirut on October 23, 1983. Wikimedia Commons

According to CIA reporting at the time, Iran had already "smuggled explosives into Saudi Arabia" at the time "and conducted terrorist operations against Kuwaiti targets."

Pointing to the 1983-1984 Beirut bombings, the agency assessed that "many Iranian leaders use this precedent as proof that terrorism can break US resolve" and view "sabotage and terrorism as an important option in [their] confrontation with the United States in the Persian Gulf."

Within a year, Saudi Hezbollah made good on its threat by attacking the Saudi petrochemical industry, which then as now employed many Americans. In March 1988, it claimed responsibility for an explosion at the Sadaf petrochemical plant in Jubail. Additional bombs struck the Ras Tanura refinery, while another apparently failed to detonate in Ras al-Juaymah.

Saudi authorities responded forcefully, arresting a number of suspected Shiite militants. They captured three Saudi Hezbollah members after a deadly standoff in which several policemen were killed and injured. The three men and another cell member were publicly executed in September 1988.

To avenge the executed operatives, Saudi Hezbollah declared war on anyone employed by "the House of Saud" and embarked on an assassination campaign abroad, attacking Saudi officials in Turkey, Pakistan, and Thailand.

Commenting on one of these plots, a CIA analysis issued in December 1988 noted, "Riyadh is concerned that the assassination of a Saudi diplomat in Ankara on 25 October may be the opening round in a Shi'a terrorist campaign targeting Saudi officials and facilities."

The Ankara shooting in question took the life of Abdulgani Bedawi, the second secretary at the Saudi embassy in Turkey. Another assassination attempt came two months later, when Ahmed al-Amri, the second secretary at the Saudi mission in Karachi, Pakistan, was seriously wounded by a gunshot in late December.

Then, on January 4, 1989, Saleh Abdullah al-Maliki, the third secretary at the Saudi embassy in Bangkok, was shot and killed outside his home. Two factions of Saudi Hezbollah claimed responsibility for the latter operation in statements released under the names "Soldiers of Justice" and "Holy War Organization in the Hejaz," both of which tied the murder to Riyadh's September 1988 executions. In February 1990, four more Saudi diplomats were murdered in Thailand in a case ultimately tied to Saudi Hezbollah.

Meanwhile, a group of Kuwaiti and Saudi Shiites affiliated with Hezbollah al-Kuwait were caught smuggling explosives into the kingdom in July 1989 and placing them in the vicinity of Mecca's Grand Mosque. That September, sixteen Kuwaitis and four Saudis were beheaded for their roles in the plot, prompting Saudi and Kuwaiti Hezbollah to call for vengeance at a press conference in Beirut, where they could speak freely under the protection of their mentor, Lebanese Hezbollah.

Several of the executed Kuwaitis were of Iranian origin; officials in Tehran called them "martyrs" and declared that their deaths should be avenged with attacks on Saudi, Kuwaiti, and US interests. A CIA analysis published in August 1990 assessed that "these statements may have encouraged radical Shia elements to carry out a series of attacks against Saudi facilities and personnel." The agency also assessed that Iranian-linked terrorist attacks carried out over the previous year "were probably approved in advance" by the president and other senior leaders.

A supporter of Lebanon's Hezbollah leader Sayyed Hassan Nasrallah holds up a poster of him as he appears on a screen to speak at an event to commemorate the deaths of six Hezbollah fighters and an Iranian general killed by an Israeli air strike in Syria on January 18. Khalil Hassan/Reuters The most well-known Hezbollah attack on Saudi interests was the June 1996 Khobar Towers bombing, which killed 19 US servicemen and an unspecified number of Saudi civilians in a nearby park and wounded another 372 Americans.

Although responsibility for the attack was unclear at first, the FBI ultimately concluded that the bombing was planned, organized, and sponsored by Iran and executed by Saudi Hezbollah operatives, prompting US federal indictments against thirteen members of Saudi Hezbollah and an unidentified Lebanese Hezbollah operative.

Another kind of shadow war

While Hezbollah remains an active agent in Iran's shadow war with the West, the regime's most recent plots targeting Saudi interests have been planned and executed by the Qods Force. Like the Hezbollah assassination campaign in the late 1980s, recent plots have included the targeting of officials abroad.

In May 2011, Iranian agents shot and killed another Saudi diplomat in Karachi, foreshadowing the Washington restaurant plot that was already being planned at the time. In June 2012, Kenyan authorities arrested two Iranian nationals — purportedly Qods Force operatives — believed to be plotting attacks on Israeli, US, British, or Saudi targets in Kenya or elsewhere in Africa.

Indeed, the Qods Force reportedly established a dedicated "Special External Operations" entity known as "Unit 400" to carry out just these types of attacks, primarily targeting diplomats from countries that were actively trying to undermine Tehran's nuclear program.

Cyberwarfare seemingly entered the rivalry at this point as well — in August 2012, the state-owned oil company Saudi Aramco was hit by a cyberattack that US intelligence attributed to Iran, with then-defense secretary Leon Panetta describing it as "a significant escalation of the cyber threat."

Lebanon's Hezbollah leader Sayyed Hassan Nasrallah meets with Ali Akbar Velayati (L), Iran's Supreme Leader Ayatollah Ali Khamenei's top adviser on international affairs, in Beirut in this handout picture released by Hezbollah Media office on May 19, 2015. REUTERS/Hezbollah Media office The regime seemed to put this shadow war on hold while the multilateral nuclear negotiations unfolded, but current sectarian tensions in the region may have rekindled Tehran and Hezbollah's interest in targeting their Saudi adversaries with asymmetric and reasonably deniable attacks.

Regional tensions were already high over Riyadh and Tehran's support for competing actors in Lebanon, Syria, and Iraq. But Riyadh's leadership of a military coalition targeting Yemen's Houthi rebels — who practice Zaidi Islam, a branch of Shiism — came as an unwelcome surprise to Iran (for more on Tehran's links to the Houthis, see PolicyWatch 2364, "Yemen's Zaidis: A Window for Iranian Influence").

Understood against the background of numerous past Iranian and Hezbollah attacks on Saudi interests, the latest warnings constitute much more than just isolated semantic barbs in the war of words between Riyadh and Tehran. Given this history and the very real Sunni-Shiite tensions engulfing the region, Naim Qassem's April 13 pledge — that Hezbollah "cannot be silent" about the Saudi "genocide in Yemen" — may lead to more than just angry statements.