Is regime change in Syria back on the US agenda?
For most of Syria’s six-year civil war the US has been pushing for the departure of Bashar al-Assad, even if former president Barack Obama was unwilling to use military options to remove him.
Donald Trump had conspicuously backed away from that stance, with his administration describing Assad’s rule as “political reality” shortly before the chemical weapons attack.
His team have been careful to present Friday’s missile strikes as a contained response to a specific atrocity, intended as a deterrent to further chemical weapons use. But Trump is nothing if not unpredictable.
Could there be follow-up attacks from the US?
Russia has already said it will help Syria boost its air defences, a clear signal to Washington that further intervention carries a serious risk of escalation, particularly as Moscow has also threatened to cancel a military coordination hotline.
Syrian and Russian radar, air defence systems and fighter jets could potentially limit the impact of future missile attacks while making any mission with manned planes dangerous for pilots.
But by choosing to redraw the US “red line” over chemical weapons Trump has put US military prestige on the line. If there are further attacks with chemical weapons, it would probably be politically and personally difficult for him not to order a response.
Will the campaign against Islamic State be affected?
In the short term, the push for Raqqa and Mosul, the final two urban strongholds of Isis, is unlikely to be seriously affected.
Neither Trump nor his generals are likely to want to decelerate a campaign they hope is moving into its final stages, particularly since Trump has put fighting the extremist group at the heart of his presidency.
The threat to suspend coordination on military efforts between Moscow and Washington may make bombing raids somewhat more risky, but there had been limited overlap between Russian and western coalition efforts anyway.
The Russian military has supported Assad’s troops, more frequently in fights with other rebel groups than in battles with Isis. The US-led coalition is only bombing Isis, and supporting non-regime military groups.
Will Russian support for Assad remain firm?
Russia has often said its support for Assad is conditional. Moscow’s desire for a sympathetic government in Syria is likely to be more important than the survival of the Syrian president himself.
But in a country fractured by war, there are few obvious alternatives, something Assad may be counting on when he takes risks like a chemical weapons attack.
Russia’s strategic interest in backing the Syrian regime, and its willingness to use every tool at its disposal to support Assad – from its jets to its UN security council veto, means he is unlikely to be dislodged any time soon.
Assad is also bolstered by Iran, a major regional power. Baghdad does not want to see Syria controlled by rebels close to hostile Sunni Arab states.
Do these missile strikes mean an end to Trump’s ‘reset’ of relations with Russia
Trump came to power promising a reset of ties with Russia, and openly expressing his admiration for president Vladimir Putin.
His victory was welcomed in Moscow, which is suspected of having tried to meddle in the US election to support Trump. Since then, links between Moscow and key members of his campaign team and administration have been under heavy scrutiny.
The military strikes, accompanied by blunt criticism of Russia’s failure to stop Assad deploying chemical weapons, appear to have upended that relationship.
Trump’s secretary of state, Rex Tillerson, heads to Moscow in a few days. The welcome he gets may provide a clearer indication of whether Russia feels the missile strikes on Shayrat airbase have irreparably damaged ties.
It’s possible that after investing heavily in Trump, Putin may want to try and contain disagreements over Syria and focus on bolstering the overall relationship with cooperation in other areas.
What are the military risks if the US is drawn further into the Syrian conflict?
If the US decides to carry out further strikes, or take other military action against Assad, one of the main worries it that it could hit a Russian plane or soldiers.
Moscow was notified of Friday’s strikes before the missiles were launched, giving it time to evacuate troops. But Russia is threatening to suspend the hotline used to deliver that warning and there may be Russians near many potential targets in Syria.
If the US hits a Russian target, even by accident, there is a risk of the situation escalating into a direct confrontation between two nuclear-armed powers.
Bombing raids often put Syrian civilians in danger in conflict zones, as recent tragedies in Mosul and near Raqqa have shown. And any US military commitment that goes beyond guided missiles could also put the lives of US soldiers at risk.
What are the political risks of greater US involvement in the Syrian civil war?
One of the questions those opposed to Assad’s rule have struggled to answer for years is what Syria would look like if he was removed.
Assad’s ruthless brutality and the long war have bred a fractured, radicalised opposition on the ground. It is dominated by hardline Islamist groups who would like to turn the country into a Sunni theocracy.
After years of fighting they are unlikely to hand power to the moderate political exiles more palatable to western powers.
Nor is it clear that any successor given control by edict could hold the country together; the fate of Iraq after Saddam Hussein and Libya after the overthrow of dictator Muammar Gaddafi have haunted efforts to push for change in Syria.
The struggle to imagine a Syria without Assad was one of the main reasons Obama was reluctant to intervene in support of rebels, and that has not changed.
US ability to project power, badly damaged by the disastrous outcome of the Iraq invasion, could also be at stake, along with the country’s slowly recovering economy.