By Michael Knights Best Defense guest columnist – ForeignPolicy – This article represents the opinion of the author-

When asked to address the question of what a Saudi-Iran war would look like, my first instinct is to ask the reader to look around because it is already happening. As the futurist William Gibson noted, “the future is already here — it’s just not very evenly distributed.” Already, Saudi Arabia and Iran are killing each other’s proxies, and indirectly are killing each other’s advisors and troops, in Yemen, Syria, Bahrain, and Saudi Arabia’s Shiite Eastern Province. The future is likely to look similar. The existing pattern will intensify, eventually spill over in a short, sharp direct clash, and then sink back down again to the level of proxy wars in other people’s territories. The preferred method of conflict between these states has for a long time been proxy warfare. Since its devastating eight-year war against Iraq, the leadership in Tehran has demonstrated a strong preference for acting through proxies like Lebanese Hezbollah, the Iraqi Shiite militias, and Hamas. Lacking a strong military for most of its existence, the state of Saudi Arabia has likewise used proxy warfare to strike painful blows against its enemies, notably against Egypt’s occupation forces in the 1962-1970 Yemeni civil war and against the Soviets in Afghanistan. Both these players try to get others to do most of their fighting and dying for them.

Iran’s powerful support for Shiite militias is well-documented. Lebanese Hezbollah has evolved into a central pillar of Iran’s retaliatory capability against Israel, and more recently has answered Iran’s call to provide reliable ground forces to prop up the Assad regime in Syria. Lebanese Hezbollah is no militia: It has Zelzal-1 missiles capable of hitting Tel Aviv. Hezbollah has large stocks of advanced anti-tank guided missiles and Explosively-Formed Penetrator (EFP) roadside bombs capable of penetrating any Israeli tank. Iran as also supplied Hezbollah with advanced C-802 anti-shipping missiles, which crippled an Israeli warship in 2006, and most recently with even more advanced Yakhont anti-ship missiles. Now Iran seems to have provided its Shiite Houthi allies with C-802 missiles, which have been used in a number of attacks on United Arab Emirates (UAE) warships in the Saudi-led war in Yemen. The Houthis are inflicting heavy damage on the Saudi military, destroying scores of U.S.-supplied main battle tanks and other armoured vehicles using Iranian-provided anti-tank guided missiles. Iran’s proxies are seizing terrain in southern Saudi Arabia and lobbing Scud missiles at military bases deep within the kingdom. In Iraq the Iranian-backed militias have been provided with Iranian air support, artillery, electronic warfare equipment and medical support. Badr, the main Shiite militia in Iraq, fought as a military division in the Iranian order of battle during the Iran-Iraq War. Badr now leads Iraq’s largest security institution, the half-million Ministry of Interior, and the Shia militias are being formed into a proto-ministry that resembles their patron, Iran’s Islamic Revolutionary Guard Corps (IRGC). The “Hezbollah-ization” of two key regional states is well-underway.

Most worryingly for Saudi Arabia the Iranian bloc is demonstrating a disregard for long-lasting “red lines” over Bahrain and Saudi Arabia’s oil-rich Eastern Province, which has a majority Shiite population. In 2011 Saudi Arabia and the UAE deployed scores of main battle tanks and armoured personnel carriers to directly safeguard the Bahraini royal family in the face of Arab spring uprisings. This robust move seemed to deeply shake Tehran, triggering the hapless Iranian plot to assassinate Adel Jubeir, the Saudi Arabian ambassador to the United States. In the last year Iran seems to have been acting increasoingly recklessly in Bahrain and Saudi Arabia’s Eastern Province. Iraqi Shiite militias like Badr spin-off Kataib Hezbollah have worked with Iranian-backed cells in Bahrain and Eastern Province to import advanced EFP munitions in large numbers with the evident intent of giving Shia communities the ability to self-defend against future Saudi military crackdowns. This kind of game-changing behaviour by Tehran is undoubtedly one reason the Saudi government chose to recently execute Eastern Province Shia dissident Sheikh Nimr al-Nimr. Long before the current hullabaloo Saudi Arabia and the other Sunni Gulf States have been slowly cultivating their own network of military proxies. The first major recipient of Gulf military support was the Saudi-supported Lebanese government. The UAE sent nine fully-armed and crewed SA-342L Gazelle helicopters to help the Lebanese government crush Al-Qaeda-linked Fatah al-Islam at Tripoli’s Nahr al-Bared refugee camp in May 2007. In 2009, a year after Saudi’s King Abdullah called for the U.S. to “cut the head off the snake” by bombing Iran, Riyadh launched a nine-week military campaign against the Houthi rebels in northern Yemen, losing 137 troops. This triggered a major intensification of Saudi Arabian, Jordanian and UAE provision of training, salaries, armored vehicles, and weapons to anti-Houthi militias in northern Yemen. Now the Gulf States and other allies like Pakistan and Somalia are building up new proxy forces in Yemen to assist in the Saudi-led military campaign against the Houthis.

So what happens next? Saudi and Iran will want to test and hurt each other, signal limits, but not suffer mutual destruction. Iran will begin to stir violence in Eastern Province and Bahrain, and it may try harder to fight supplies through to Yemen by sea by bolstering Houthi coastal missile batteries. The next stage in the Saudi Arabian war with Iran will be an intensification of the proxy war in Syria. This is where Riyadh plans to fight its main battle against Iran. Then Saudi Arabian Foreign Minister Prince Saud al-Faisal signaled as far back as March 2012 that “the arming of the [Syrian] opposition is a duty.” Already Saudi, Qatari and Turkish support has allowed rebels in northwestern Syria to inflict severe armor losses on pro-Assad forces using anti-tank guided missiles. The provision of anti-aircraft missiles may be next. The U.S.-led coalition seems to be backing away from the morally-ambiguous war west of the Euphrates in Syria, where the main opposition to the Islamic State and Assad are radical Salafists that Western nations cannot engage. But Saudi Arabia and its allies have been doing exactly this in Yemen for half a decade and are now likely to take over the war west of the Euphrates in Syria. Riyadh now seems to view Al Qaeda in the Arabian Peninsula as a lesser evil to the Iranian-backed Houthis in Yemen: how soon before it views “moderate splinters” of the Islamic State and Jabhat al-Nusra the same way in western Syria?

Though neither Saudi Arabian nor Iran envisage an open conventional war between them — a result that Saudi Arabia’s crown price and defence minister Prince Mohammed bin Salman recently called “a major catastrophe” — there is always the potential for frontier skirmishes on their shared littoral borders and in the neutral space of the Gulf. Shared gas fields and disputed islands are obvious touchpoints. Iran might test missiles closer and closer to Gulf sea-lanes and coasts. Aerial patrols might begin to test each other: this happened during the Iran-Iraq War along the so-called “Fahd Line” until a Saudi interceptor shot down two Iranian fighter aircraft in 1984. Iran (or the Gulf States) could undertake tit-for-tat harassment, boarding or even deniable use of naval mines against each other’s trade routes. (Iran also used this tactic in the 1980s). Cyberwarfare is a likely deniable weapon of choice for both sides also. At some point in the coming years we are likely to see both sides miscalculate and unleash a very short, very sharp burst of military force against each other. This will be a wake-up call. Both Iran and the Gulf States are far more powerfully armed than they were during the Iran-Iraq War. The advanced air forces of the Saudis and their key ally the UAE are now capable of destroying practically all Iran’s port facilities, oil loading terminals and key industries using stand-off precision-guided munitions. Iran can shower the Gulf coastline with multitudinous unguided rockets and a higher concentration of guided long-range missiles than ever before. In 1988 the Iranian navy was destroyed by the United States in a single day of combat — Operation Praying Mantis. Even a day or two of such “push-button warfare” would serve as a reminder to both sides of their overriding imperative to avoid direct conflict and to keep their conflict limited to the territories of unfortunate third-parties. Michael Knights is the Lafer Fellow at the Washington Institute for Near East Policy. He has worked on the military balance between Iran and the Gulf States for over twenty years