Israel's weekend attacks on military targets inside Syria may prod Washington into taking further action to assist the rebels trying to overthrow the regime of Bashar al-Assad. So far, only non-lethal U.S. aid is going to the opposition forces.
Among the potentially lethal options the United States could consider are, from most likely to least likely: limited aerial operations to degrade Syrian air power and reduce military arsenals, establishing safe zones to protect opposition-controlled parts of the country, distributing weapons to moderate members of the Syrian opposition, or a full-scale, Iraq-style invasion.
An air war
Serious concern has been expressed by members of the Obama administration that Syrian air defences are much more robust than were those of Libya, and any U.S. or allied attacks by air would pay a price in casualties.
Considering how Israel was apparently so successful in attacking Syria by air, those reservations now are being discounted.
Not so fast, said Anthony Cordesman at the Center for Strategic and International Studies in Washington. "Syria does not have not strong air defences by U.S. standards but it is still very large."
"Even though the events of the past weekend may suggest air power's efficacy in responding to the civil war, it will be no easy task to expand this into a wider campaign," he added.
Retired U.S. Navy Commander Christopher Harmer agrees that Syria's air defences are very dense but noted that U.S. forces have long-range cruise missiles and aircraft that can fire safely on targets from a distance.
"We can seriously degrade the Syrian air force by hitting its aircraft, its runways and its radar, without putting any U.S. or NATO personnel at risk," said Cmdr. Harmer, an ex-fighter pilot.
No-fly zones
The United States, with allies Britain and France, demonstrated in Iraq from 1991 to 2003 that effective safe zones could be maintained in a country larger and more dangerous than Syria.
The United States has the capacity to do the same in Syria, flying out of the NATO base – with Turkish consent – in Incirlik, Turkey.
But it wouldn't even be necessary to patrol the skies, argues Christopher Griffin, executive director of the Foreign Policy Initiative in Washington. "The United States and our allies could use the Patriot missile-defence batteries now deployed in southern Turkey to establish a credible threat against Assad's air power over parts of Aleppo and Idlib provinces [in northern Syria]," he wrote recently.
And such a zone could be expanded, Cmdr. Harmer said, by the use of aircraft flying along the border and over the Mediterranean, because U.S. air-to-air missiles have substantially longer ranges than Syrian missiles. "We can shoot them down long before they get close enough to hit us," he said.
Small arms
The one aircraft that Patriot missiles and offshore U.S. fighters can't shoot down easily are Syrian helicopters that are being used against rebel forces. The best weapon to counter them are shoulder-launched, surface-to-air missiles such as the Stinger, made famous in Afghanistan for turning the tide against Russian helicopters in the 1980s.
However, that means supplying them to Syrian rebels.
Supplying any small arms to the rebels is "the last thing you want to do," argues retired Canadian Lieutenant-General Andrew Leslie, former chief of the Canadian land staff.
"Yes, there's an imbalance between Assad's forces and the rebels," he said, "but once you flood the area with such weapons, you have no idea where they'll end up, and no way of getting them back."
Especially worrisome is having the arms fall into the hands of the more extreme jihadist rebels.
Cmdr. Harmer agreed that it is a problem. "It happened in Afghanistan with the Taliban, and it happened in Libya when the weapons ended up in Mali."
"But in Syria," he added, "We have a very narrow window in which to act – while the more secular rebels are still in the majority. If we wait much longer, there will be no opposition we can work with."
Ground invasion
"If I were advising the Americans, I'd say, 'Think very carefully before you put boots on the ground,'" said Gen. Leslie, a former deputy NATO commander in Afghanistan. "You can't reliably predict what the consequences will be. Best to stay away.
"This is not a Western issue," he argued. "If the Arab League wants to go in – okay, support them, but not with soldiers on the ground."
Cmdr. Harmer agreed. "There are options that don't put American lives at risk. We should use them."
A Canadian role
In the event that a NATO force or a "coalition of the willing" were to intervene in Syria, Canada would be well-suited and well-equipped to assist in a number of areas, according to Gen. Leslie. Canada can help maintain a no-fly zone, provide cover for a humanitarian corridor, and assist in command-and-control operations.
"None of these involve the use of force, at least not in the first instance," he said, "though, obviously, we'd be prepared to fire on anyone violating a no-fly zone or attacking humanitarian relief operations."
The chemical equation
Dealing with Syria's deadly chemical weaponry is no easy matter for any power intervening in Syria.
"You can't take them out by air attack," said Cdr. Harmer. "And there's nobody, but nobody willing to send American troops to do this."
"Maybe the Israelis," he added, "if they put all their special forces together. It would maybe 1000 guys to do the job."
That's not likely either. "Basically this is Assad's get-out-of-jail card," concluded Cdr. Harmer. "It may allow him to survive."