The trickle of arms to Libya may have already begun, with the reported cargo of Britain's ill-fated task force including both weapons and explosives. The question is now whether this will turn into a flood.
The White House is mulling over whether or not to funnel weaponry to the rebels in earnest, even if it yesterday insisted that sending weapons to Libya would be illegal. The obvious precedent would be American support – in concert with Saudi Arabia and Pakistan – to arm the anti-Soviet mujahedin during the Afghan jihad. That had as its legacy the civil war of the 1990s and the insurgency that rages today. Nearly 1,000 heat-seeking Stinger missiles provided to the resistance played a key role in countering Soviet helicopters, but these later found their way to Croatia, Iran, and North Korea.
Libya's rebels would benefit from more anti-aircraft weapons, particularly as they advance westwards across open ground. Yet it is precisely these that pose the greatest risk if used against Western forces in other theatres, or by terrorists. Two such surface-to-air missiles were fired at a passenger aircraft in Mombasa in 2002.
Small arms proliferation could not only impact countries like Chad or Sudan, renewing or prolonging civil conflict, but also complicate Libya's envisioned post-Gaddafi future by empowering small armed groups who may later emerge in opposition to any constitutional settlement.
Some types of assistance may be more effective and less risky. Communications equipment, such as military radios and satellite phones, would allow dispersed military units to fight in a more coherent fashion, despite lacking training and unified command. A flow of information from Nato assets could be just as crucial.
Well-intended humanitarians should also be wary of arming groups whose composition and intentions are opaque. Afghan rebels who received external assistance are at the heart of Afghanistan's insurgency today. These include Gulbuddin Hekmatyar, who received millions of dollars from the CIA and later co-operated with al-Qa'ida, and Jalaluddin Haqqani, who wreaks havoc across eastern Afghanistan and Pakistan.
The case of the Northern Alliance is also instructive as to whether arming rebels works. Despite years of support from India, Russia and Iran, the Alliance was repeatedly outfought by the Taliban. Only when US special forces and airstrikes entered the fray did the Taliban collapse.
This is categorically not a reason to stand by as Gaddafi inflicts slaughter. But any assistance must be carefully calibrated. It is impossible to predict how the anti-regime coalition will evolve over the coming weeks of what will be a protracted war.
The writer is an associate fellow of the Royal United Services Institute