By Emile Hokayem, IISS Senior Fellow for Middle East Security.
What are the West’s military options – and what might the targets be?
Western countries have to decide whether military action in Syria is about punishment and deterrence for the use of chemical weapons, or whether they want to be more ambitious and go after the military infrastructure of the Assad regime, which has enabled his war machine to make very significant advances recently.
The likelihood is that President Trump, Prime Minister May and President Macron will opt for a narrow strike aimed at enforcing the international norm against the use of chemical weapons. If so, they face a choice between targeting the infrastructure that creates those weapons and hitting the means of delivery – the helicopters, the air force, the runways.
The problem is that the strike needs to be calibrated for deterrence, taking into account the precedent of April 2017 when the US fired 59 missiles at the Shayrat airbase. This strike needs to be bigger, because that previous attack was felt to be a failure. So the size of the operation and choice of targets are going to be critical.
How might Russia respond?
Much depends on how Russia perceives the strike, and on the nature and size of the strike. It's very likely that the US and its allies will do their utmost to avoid any Russian casualties. And certainly there's a communication channel between the US and Russia to avoid that.
Russia, however, is in a tight spot because it has to demonstrate that it can live up to its own bluster – defend its ally and inflict some damage on US missiles. But Russia also has to be very careful about not over-responding. There is no match in a direct competition between the US and Russia.
It's very possible that, instead of focusing on the US, Russia will decide to punish Syrian civilians and Syrian opposition even more. Practically, much will depend on whether Russia takes an active part in the defence of its ally – if it turns on its radars, if it mobilises its air defence and missile defence systems to protect Assad. The Russians have to calculate very carefully.
How likely is escalation?
Direct escalation is unlikely, though if it happens it could have massive consequences. What is likely is indirect delayed escalation, where Russia, Iran and the Assad regime decide to make Syrian rebels and civilians pay, but also over time increase targeting of US troops based in eastern Syria or Iraq.
How will Iran and Israel react?
Israel has been intervening militarily in Syria, but its interests and those of the US are not fully aligned. The US would be intervening in Syria to punish the Assad regime for its use of chemical weapons and deter further use. Israel, however, is not targeting Assad’s regime per se. Instead it’s focused on what it sees as spreading Iranian influence, military buildup inside Syria and support for Hizbullah and other Iran-friendly forces inside the country.
Israel has been deeply troubled by what it has seen, but it has a good intelligence and has conducted air strikes inside Syria for years now. It will continue to pursue its strategy regardless of what the US does. The question is whether Iran will retaliate against the US by hitting Israel. Certainly, this is a possibility. Iran sees Syria as a defensive front line against Israel. The two sides are locked in a logic of force and deterrence that is quite fragile.
Is this a pivotal moment for US leadership in the Middle East?
Yes and no. US leadership in the region has been waning for over a decade as a consequence of the Iraq war, the dithering of the Obama administration (especially in Syria in 2013) and now Trump.
The Trump administration is walking a very fine line because of the bombastic statements of Trump himself and the confrontational anti-Iran tone of John Bolton and Mike Pompeo. All this has set high expectations about what the US can do. But Trump is of two minds. He talks about striking the Assad regime even as he talks about leaving eastern Syria. There is a real incoherence.
It would be a very complex situation for the US to navigate under any circumstances, because the battlefield in Syria is so much more complicated than it was before. What makes it harder is the sense of disarray within the Trump administration, with conflicting messages all the time. Outsiders are concerned that the administration is not well-equipped to handle a conflict and prevent catastrophic escalation.