The Kremlin’s announcement on Thursday that a hotline between Russia and the US on Syrian matters was active drew attention to the longstanding practice of “deconfliction”.

The term refers to attempts to avoid misunderstandings and potential direct clashes between Russia and the west in Syria, where for years Russia has been targeting Syrian opposition forces, and western coalition planes have been operating largely against Islamic State targets.

The deconfliction hotline, established in 2016 between US central command in Qatar and its Russian equivalent in Syria, has on occasion been shut down due to disputes between Moscow and Washington.

The prospect of imminent US-led strikes on the Syrian regime in response to Saturday’s chemical weapons attack outside Douma puts a great deal of pressure on the deconfliction process.

There is some evidence that key figures, such as the UN secretary general, António Guterres, are working hard behind the scenes to see how any conflict can be contained, on the assumption that the US is determined to press ahead.

The US will be required to give Russia some advance notice of its intentions, giving it a choice about whether to extricate itself from Syrian positions.

In public, apart from pronouncements by the French president, Emmanuel Macron, and the contradictory tweets of his US counterpart, Donald Trump, little has been said by western leaders about the purpose or scale of the strikes.

In theory, there are three potential options:

A minimalist punitive strike, similar to the US attack on the Sharyat airbase in April 2017, when three US warships fired 59 Tomahawk cruise missiles in response to a chemical weapons attack in Khan Sheikhun.



An attempt to prevent Syrian efforts to use chemical weapons again by destroying the relevant facilities and means of delivery, and by imposing a deterrent punishment.

An attempt to weaken the entire Syrian military infrastructure or even attack the presidential palace and Syrian divisional headquarters.

As it stands, there is no appetite in western capitals to dislodge President Bashar al-Assad from office, leaving some version of the middle option the most likely course of action.

Barack Obama’s abandoned attack on Syria in 2013 had intended to use at least 150 Tomahawk missiles directed at the Syrian air force command and control. But it is not possible simply to dust down those plans because of the presence of roughly 2,000 Russian troops, who have been stationed in Syria since 2015.

Russian forces are concentrated at the Khmeimim airbase, on the outskirts of Latakia, and the Tartus naval base, but there are troops at other bases, some of them fighting as mercenaries.

Western intelligence will therefore have to be good enough to ensure missiles aimed at chemical facilities do not hit groups of Russian troops. Russia also has sophisticated air defence systems.

Further complicating the battleground picture, Iran and its militia backers have increased and entrenched their forces in Syria since 2013.

Ben Barry, a senior fellow at the International Institute for Strategic Studies, in London, said it would be possible for Russia, with advance notice about targeting from the west, to remove its personnel from likely targets. Similar warnings were given to the Russians before the attack in 2017.

Barry pointed out that most of the key weapons at the west’s disposal could be fired from aircraft carriers and submarines, and there was no need for coalition jets to enter Syrian airspace.

There was, however, a risk of an accident, Barry said, because Russian advisers could be attached to Syrian forces down to battalion level.

A key question for the US and its allies, Barry said, was whether they could put together a package of identifiable chemical weapons-related targets. Chlorine, for instance, is a baseline chemical that does not require very sophisticated laboratories to produce, unlike, say, sarin.

Barry drew attention to other legitimate chemical weapons-related targets, such as the delivery infrastructure, including helicopters, airbases and some scientific research labs in Damascus.

Justin Bronk, a research fellow at the Rusi thinktank, said: “Destroying the Syrian air force’s means of delivery – its jets and helicopters – would require far more than cruise missiles. It would require a concerted, large-scale air effort involving hundreds of fighters, bombers, jamming aircraft and intelligence, surveillance and reconnaissance.”

The dilemma for the US and its allies is whether to mount a small strike that might not have a sufficient deterrent effect or a large strike that risks hitting Russian troops and dramatically increasing tensions.