America's sudden onslaught against Syria has taken the world by surprise. The White House is said to have blocked the Pentagon's preliminary planning for a military assault on the country, and earlier this week the prime minister assured the House of Commons that there were "no plans for an attack on Syria" - language eerily reminiscent of that used about Iraq last autumn. Something must lie behind all this.
The charges are hardly earth-shattering. Syria is accused of harbouring Iraqi fugitives. Possibly so. The Syrians opposed the invasion of Iraq. The Syrian authorities cannot prevent Iraqis getting across a 400-mile desert border. It would not be surprising if, rather than accept the humiliation of handing them over to the Americans, they ushered unexpected guests towards an aeroplane.
It would be hard to describe Bashar al-Assad in such terms.
If Syria has chemical weapons, it is for a good reason - as a second-strike capability against Israel. It is inconceivable that the Syrians would strike first, knowing the Israelis would immediately go for nuclear retaliation.
The third American allegation is an old chestnut - that Syria is a rogue state supporting terrorism.
The Syrians have long given hospitality to the political wing of Palestinian rejectionist movements. They permit the Iranians to channel through Damascus airport the arms required by Hizbullah in south Lebanon. These are regarded as potential levers in negotiations with Israel for return of the occupied Golan Heights. They also give Syria some measure of influence over the Palestinian and Hizbullah resistance. This is tough diplomacy, Middle East style; it hardly amounts to being a rogue state.
The most straightforward explanation for the American campaign is that it is an effort to deter the Syrians from granting sanctuary to fleeing Iraqis. But there must be more to it. Perhaps the Americans have suddenly woken up to the fact that Syrian hostility could destroy their attempts to stabilise Iraq in the months to come.
The American invasion of Iraq was intended to "decapitate the regime". In fact, it has knocked the stuffing out of the entire system of government. Saddam's reign was one of terror imposed from above. All those involved were corrupt and most had blood on their hands. The families of their victims will be out to kill them at the first opportunity. They have no alternative but to run for their lives.
In a further twist, the Sunnis live in fear that the Shia majority who they have oppressed for decades will turn against them. That is why the doctors, at least those who were Sunni, abandoned their hospitals in the face of gangs of looters, most of them Shia.
The apparent ease of the military victory is extremely deceptive. Iraq is now on the verge of anarchy. The first requirement is to impose some measure of order, the second to re-establish a skeleton administration that can distribute humanitarian aid effectively.
Then begins the task of assembling some kind of political structure. This will take months, if not years.
Meanwhile, there is every risk that American and British troops will be seen as an occupying force, and become targets for sniping and suicide attacks.
If Syria were to turn a blind eye to a flow of weapons and volunteers across her border with Iraq, the security situation could degenerate very quickly. Indeed, we could find ourselves in a quagmire.
The Syrians could well be in a position to block our efforts to create what Tony Blair described as "a peace worth the war". They might be tempted to do so. What Jack Straw calls "the new reality" looks to them like an American puppet state in Iraq that might settle with Israel at the expense of the Syrians and Palestinians.
Indeed, the Arabs see a deeper plot and they may not be entirely wrong.
Some members of the Bush administration came into office determined to overthrow Saddam, occupy Iraq and extend American control through as much of the region as possible.
For these officials, some of them close to the Likud party, the invasion of Iraq was only a first step intended to pave the way for the removal of Syria as the last strategic opponent of Israel.
These are some of the explanations for the sudden attempt to intimidate the Syrians.
The American campaign may make President Assad more cautious, but the Syrians are not easily intimidated.
What is clear is that the rest of the Arab and Muslim world will be deeply antagonised by such tactics.
If our primary aim is to counter Islamic terrorism by diminishing the mass support on which it thrives, this is hardly the best way to go about it.
· Sir Andrew Green was UK ambassador to Syria from 1991-94 and to Saudi Arabia from 1996-2000