The shifting rules of war
The Gulf crisis poses significant questions about the future of conflict, writes Dominic Nicholls
While the US insists Iran would face "obliteration" in the event of war, the reality may not be so simple. The US is already in gear for an attack through its 5th Fleet based in the Gulf. It may decide to launch a limited strike against Iranian radar sites dotted along the coast of the Persian Gulf, as Donald Trump almost did last week following Tehran's downing of a US Navy drone.
Just as the US (along with Britain and France) launched missile strikes into Syria in April 2018 in response to the use of chemical weapons, Donald Trump may want to employ limited force, probably with a warning through diplomatic back channels so as to avoid loss of life, to send a proportionate response.
If a full-blown conflict erupts, the US would seek to flatten the Iranian military, first by taking down air defences. But Iran only needs to inflict enough damage, for long enough, to convince the US public they are heading into a quagmire.
There are many ways they can strike back.
Iran's reach in the Gulf - and particularly in the Strait of Hormuz, through which passes almost 20 per cent of the world's oil and a third of its natural gas - poses a significant threat.
Though Iran's military power is outstripped by that of the US in the area, the Islamic Republic is capable of manipulating shipping through the use of naval mines and, given the Strait of Hormuz is only 24 miles wide at its narrowest point, land-based missiles would have what military professionals call a "target-rich environment".
The Centre for Strategic International Studies says Iran uses missiles as a central tool of power projection, particularly for anti-access and area denial capability. According to the think tank, Tehran possesses the largest and most diverse missile arsenal in the Middle East, with thousands of short and medium-range weapons.
It also has newly enhanced military capabilities. In February Iran test-fired a Nasr-1 anti-ship missile from a submarine in the Gulf. With a 20-mile range, it can cripple ships of up to 1,500 tons. John Miller of the International Institute for Strategic Studies calls it a potential "game changer".
According to Prof Michael Clarke of the Royal United Services Institute, "Iran uses the Gulf as a tap to turn on the tension." It could decide a limited military strike in the Gulf, albeit with the attendant risk of escalation, would be an appropriate next step.
Iran may instead decide to increase the use of proxy forces, or give extra financial or material support to Hizbollah across the Middle East, fuelling a much wider conflict. Despite tough talk and deployment of 1,000 additional US troops, Mr Trump himself seems much more interested in renegotiating the nuclear deal than in actual conflict with Iran.
Rules of warfare and proportionality seem to be shifting. Mr Trump, in a telling comment, said of the downing of the surveillance drone: "We didn't have a man or woman in the drone. It would have made a big difference". Even 20 years ago, such a hostile action would have been seen as an act of war. But as military might is increasingly deployed through autonomous systems, the point at which competition becomes conflict is no longer clear.
If the world is in a perpetual state of contest, with the occasional outbreak of actual combat, is the shooting down of a drone seen as an act short of war?
And if on a spying mission but located in international airspace, is it a legitimate target? Is the taking of human life now the line beyond which a state of war is understood to exist?
If so, what permissions would that bestow on a country seeking to undermine another state through cyber attacks?
The crisis in the Gulf poses a clear and present danger to regional stability and the global economy. But it is also asking some significant questions about the future of warfare.