Syria: Questions facing the West

What is the objective?

There are two main options. The US and its allies could punish President Bashar al-Assad for using chemical weapons and deter their future use.

Or they might go further and try to destroy his regime. The former would be a relatively brief campaign against important military targets; the latter a sustained, Kosovo-style operation lasting weeks or months. The fact that the UK is suggesting action in a week or so suggests the aim will be punishment, not regime change.

What about the UN inspectors?

A 20-strong team of UN experts has arrived in Damascus to investigate whether chemical weapons had been used. On Monday, they were allowed to visit the sites of last week's attacks but were shot at by snipers on the way. Their mandate restricts them to finding out whether chemical weapons were used - which is no longer in dispute - not who was responsible.

Will the experts achieve anything useful?

Possibly. They might be able to establish which chemical agents were used. The regime is known to possess stockpiles of mustard, sarin and VX nerve gases. If the UN finds that any of these were used, it would imply that Assad forces were responsible.

What might be the targets of allied air strikes?

It will depend on the objective. If the aim is punishment, then all the strikes are likely to be at long range. No aircraft would fly over Syria, removing the need to suppress air defences. The targets would probably be important military installations, such as arms dumps, air bases and communications centres.

If, however, the US and its allies decide to topple Assad by changing the balance of the civil war, a far wider range of targets will have to be hit.

They will start by destroying air defences and then move on to military bases and sites connected with regime power.

What about chemical weapons stockpiles?

They could be targets whatever the option chosen. However, unless the attacks totally vaporise the chemical weapons, there would be a risk of dangerous leaks. Damaged stockpiles might be left vulnerable to plunder by rebels and terrorist groups, including al-Qaeda.