The US cruise missile strike on Syrian forces in response to Syrian President Bashar al-Assad’s use of chemical weapons against his citizens has distinguished US President Donald Trump’s approach to using military force from that of his predecessor, Barack Obama. That could potentially change calculations from Beijing to Moscow to Pyongyang. Trump’s administration has set a long-term goal of forming an international coalition to remove Assad. Thursday night’s missile strike, however, also highlights the limited military options the US has to achieve Assad’s undoing.


Can the US just use more cruise missiles?
It could. Cruise missiles would probably again be the weapon of choice if the Trump administration decides to punish Assad for any future transgression. The Raytheon Co Tomahawk missiles used in Thursday’s attack have some strong advantages: They’re hard to shoot down, pose little if any risk to US personnel and can deliver a 1,000-pound warhead from a distance of up to 900 nautical miles. A missile attack can reduce the Assad regime’s air superiority, which it has used to drop chemicals and barrel bombs, unguided containers filled with explosives, on civilians. According to the International Institute for Strategic Studies, Syria has about 280 combat aircraft, but few are operational. Russian state television said nine Syrian planes were destroyed in the US attack.


Can cruise missiles be used for a wider campaign?
Perhaps, but cruise missiles can’t solve all military problems. First, they are best used against fixed targets. The latest generation Tomahawks deployed on Thursday can be guided after launch, but that requires real-time intelligence from the ground or from aircraft flying over the target, both of which can be difficult to arrange in Syria. It also takes a lot of missiles to deal with any complex target, and missile numbers are limited. For Thursday’s attack, for example, the US used 59 Tomahawks to destroy a relatively small air base. The US Navy destroyers that fired them can carry between 30 and 50 missiles each, according to Justin Bronk, an air power specialist at the Royal United Services Institute, a think tank in the UK, whose military also uses Tomahawks. “At that rate you quite quickly deplete your stocks of cruise missiles and have to rotate ships,” he said. Plus, Tomahawks aren’t cheap. The Pentagon budgeted $226.7mn to buy 100 of them in 2015. 


Could the US use aircraft for a wider campaign in Syria?
This is controversial. Even before Russia entered the Syrian war in September 2015 to prevent Assad’s defeat, then chairman of the US Joint Chiefs of Staff General Martin Dempsey told Congress that the US military assessed Assad as having “one of the most highly developed air defence systems in the world.” True, Israeli aircraft have successfully entered Syrian airspace to attack specific targets on numerous occasions since the war began in 2011. But since 2015, Syria’s air defences have been augmented by advanced S-300 and S-400 anti- aircraft systems, owned and operated by Russia. On Friday, a Russian official said Syria’s air defences would be strengthened further. So the hurdles then President Obama faced in 2013, when he ultimately decided not to conduct airstrikes against Assad in response to a previous use of chemical weapons, are now higher. Not only is there a greater threat to US pilots, but there’s a danger of direct conflict between two nuclear powers. On Friday, Russia upped the risk further, saying it would end an arrangement to ensure Russian planes helping Assad and those of a US-led coalition attacking Islamic State in Syria don’t come into conflict.


Could the US impose a no-fly zone?
The idea of creating of a safe or no-fly zone for Syria has been floating around for a long time, and on Thursday White House spokesman Sean Spicer said Trump had been discussing the idea with regional leaders. Since Russia became involved in the war, however, the hurdles to building one have risen. That’s because if a Russian aircraft flies into the zone to conduct airstrikes, the US would have to shoot down the plane or accept that the zone can’t be protected, said Bronk. Even if Russia didn’t make a show of entering the zone, it flies many of the same aircraft as the Syrian air force; US identification systems can determine what kind of plane is flying, but not its nationality. As a result, he said, a no-fly zone could only be enforced with Russian cooperation or acquiescence, which would probably come at a very high diplomatic cost - such as giving the Kremlin what it wants in Ukraine, namely acceding to Russia’s annexation of Crimea and granting Russia a veto over Ukraine’s economic and security ties.


Could an air campaign 
remove Assad?
Any air campaign would have to rely on a force on the ground to take territory. While it might have been possible to shape moderate Syrian opposition forces into an effective ground force closer to the start of the war, that would be extremely challenging now, given how much territory they have lost and how strong radical Islamist fighters have become. Until the latest chemical weapons attack, the Trump administration appeared to be coming around to the Russian view that Assad would have to stay in place if Syria wasn’t to fall into the hands of radicals linked to Islamic State or Al-Qaeda. But after the chemical- weapon attack in Syria’s Idlib Province on April 4, which killed more than 70 people, Secretary of State Rex Tillerson said steps are underway to form a coalition to remove him. He suggested, though, that would happen only after the defeat of Islamic State.


What would it take to 
remove Assad?
The Institute for the Study of War, a Washington think tank, argues for a much more proactive US approach. It would involve creating a safe zone in the south, along Syria’s border with Jordan. The goal at first would be to build the leverage the US would need to push Assad and his allies Russia and Iran to negotiate a settlement, said Jennifer Cafarella, a Syria analyst at the institute. Ultimately, however, the US would have to decide whether removing Assad is a vital national interest, she said. That’s because although the US has the capability to defeat Russian and Syrian air defences, “you cannot just go to war in Syria with Syria, because the regime is so deeply connected with Russia and Iran. If you go to war with one, you go to war with all of them.”