Qassem Soleimani’s assassination in an American attack at Baghdad airport, on US President Donald Trump’s orders, could be a prelude to a full-scale war between the US and Iran despite the reluctance of both sides to enter into direct confrontation.

As commander of the Islamic Revolutionary Guard Corps’ Quds Force since 1998, Soleimani was the mastermind behind Iran’s regional strategy and in charge of its foreign military operations as well as those of its allies and proxies in Iraq, Syria, Lebanon and Yemen. One of his major achievements was to help the Assad regime regain control of much of Syria from opposing forces that were supported by several outside powers including the United States.

His assassination is a dramatic escalation in the ongoing US–Iran confrontation. Former US vice-president Joe Biden, now a Democrat aspirant for the presidency, said of Soleimani’s assassination that ‘President Trump just tossed a stick of dynamite into a tinderbox’.

Most experts believe that the Iranian reaction will take the form of asymmetric warfare, as Tehran knows it will be devastated in a conventional war with the US. Iran has mastered this art of indirect confrontation, and created a network of proxies able to carry out attacks that cannot easily be traced to Iran itself.

It’s too early to predict with any certainty the exact nature of the Iranian response and that of its allies and proxies. That such a response will take place was clearly indicated by Supreme Leader Ayatollah Ali Khamenei’s statement that Iran will exact ‘harsh revenge’ for Soleimani’s assassination.

Iran has several retaliatory options. In theory, its most effective would be to unleash Hezbollah, which now possesses more than 100,000 rockets that it can launch against Israeli targets. But it’s unlikely that Iran will choose this option, as it will certainly lead to harsh Israeli retribution that could severely destabilise Lebanon, which is already on the verge of state failure. Moreover, Hezbollah is not just a stooge of Tehran. It is an autonomous actor whose leadership is very wary of providing Israel the excuse to once again destroy most of its infrastructure, which it has rebuilt after it was demolished by Israeli attacks in 2006.

Iran’s proxies in Iraq, the Shia militia groups, are likely to be Iran’s first choice as there are several soft American targets, both civilian and military, in Iraq. There are still 5,000 American troops in Iraq and a large diplomatic mission that could become the focus of such attacks. The assault on the American embassy last week by supporters of the Shia militia, Kataib Hezbollah, foreshadows what could happen on a much larger scale once Tehran gives the signal for such attacks.

Saudi and other Gulf oil installations are very vulnerable to Iranian-sponsored attacks, as was demonstrated by September’s assaults on major Saudi oil facilities. A repetition of such attacks on a larger scale that could not be directly attributed to Iran is likely to form part of the Iranian retaliatory strategy.

The US has a huge number of military assets in the Persian Gulf. The Al Udeid air base in Qatar and the headquarters of the Fifth Fleet in Bahrain are two of its major bases. There are US military installations and troop concentrations in Kuwait and Saudi Arabia as well. Any of these could become targets of sabotage or missile and drone attacks. Iran would consider this fair game now that the US has moved from covert to overt targeting of Iranian assets.

Iranian attempts to block the Strait of Hormuz—sending oil prices skyrocketing—can also not be ruled out. With Iranian oil exports close to zero, Tehran will not suffer much from such a blockade but other Gulf exporters (all of whom are US allies) will suffer greatly if Iran is able to force even a temporary closure of the strait.

The impact of Soleimani’s killing will not be limited to Iran. Iraq was the scene of the assassination and it has heightened anti-American feeling there, especially since the drone attack killed not only Soleimani but also the deputy head of the Iraq’s Popular Mobilisation Forces, Abu Mahdi al-Muhandis.

Iraqi Prime Minister Adel Abdul Mahdi called the assassinations an act of aggression and a breach of sovereignty ‘that will lead to war in Iraq, the region, and the world’. He went on to say that the strike ‘violated the conditions of US military presence in Iraq and should be met with legislation that safeguards Iraq’s security and sovereignty’.

Iraq’s parliament has already passed legislation calling for all American forces to leave the country in the wake of Soleimani’s assassination.

If this occurs, it could put an end to the US military presence in both Iraq and Syria. American bases in Iraq are essential to support and supply its much smaller presence in Syria. Such an outcome will be a major victory for Iran, leaving Tehran unchallenged as the external power with the most significant ability to influence Iraq.

While all-out war may not be imminent, asymmetric warfare and the cycle of action and reaction that it will entail could easily get out of hand and lead to a full-scale conflict that neither Washington nor Tehran desires. In assessing the possible consequences, it’s worth recalling that the killing of Archduke Franz Ferdinand in June 1914 in Sarajevo led to a devastating conflagration that no one had anticipated.