Counting the cost of Nato's mission in Libya
As Nato ends its mission in Libya, just how many civilians lost their lives in the air strikes? As the BBC's Jonathan Beale explains, we may never know.
The famous phrase, attributed to Mark Twain, is that there are "lies, damned lies and statistics".
In war, establishing the truth is even harder.
As the dust settles on Nato's seven-month mission over Libya, there are few reliable statistics.
No-one is really sure, at least for now, how much this war has cost in human lives.
Estimates of those killed - including pro-Gaddafi forces, "rebel" forces and civilians - currently vary between 2,000 and 30,000.
Given that the United Nations' mandate for the mission over Libya was to "protect civilians", the Nato alliance has always maintained that it took every precaution to avoid such casualties.
The alliance says precautions often included round-the-clock surveillance from the air to establish "patterns of life" to ensure that civilians would not be hit.
On a number of occasions, planned air strikes were called off at the last minute because of fears that civilians could be hidden among legitimate military targets.'Murderers and barbarians'
To avoid undermining the mission, the alliance also relied heavily on "precision" weapons - bombs and missiles with "low collateral damage" guided by either laser or GPS systems.
The RAF's Chief of the Air Staff, Sir Stephen Dalton, told MPs last week that these weapons "performed well above the predicted level". In one example, more than 98% of Brimstone missiles fired by RAF warplanes directly hit their target. The few that did not, still landed within a few yards.
But Nato did not only use precision munitions.
British Army Apache ground attack helicopters - used later in the campaign - fired some 4,000 rounds from their 30mm cannon. It is a weapon designed to provide an arc of fire, and its use in Afghanistan has been responsible for a number of civilian casualties.
However, once again, there is no hard proof that the Apaches used in Libya led to any civilian deaths.
Throughout the seven-month campaign, Nato admitted there had been one weapon "malfunction".
On 19 June, several civilians were reported to have been killed when a missile hit buildings in Tripoli. A Nato spokesman later said that "a potential weapon system failure occurred and this caused the weapon not to hit the intended target".
Even then, the alliance has disputed claims by the Gaddafi regime that civilians were the victims of its air strikes.
An attack on what Nato says was a command and control centre in Surman on 20 June reportedly killed two children and their mother.
It was this strike that prompted Colonel Gaddafi to take to the airwaves to denounce Nato as "murderers and barbarians".
Claims by the regime that Nato had killed hundreds of civilians became part of its propaganda to try to halt the bombardment.
In the middle of July, the Libyan health office claimed the air strikes had killed 1,108 civilians and wounded 4,500. But, again, no-one has been in a position to verify these claims.'Revenge killings'
No-one within Nato, though, can claim that its air strikes did not cause any civilian deaths.
Much of the fighting took place in built-up areas and a known tactic of pro-Gaddafi forces was to hide among the civilian population.
The sheer scale of the Nato bombing campaign - with 9,658 strike sorties - suggests that it would have been very hard to avoid civilian casualties.
The UK alone - carrying out one-fifth of the total strike sorties - fired 1,420 precision-guided munitions, and hit more than 600 targets.
In September, the Royal United Services Institute (RUSI), an independent think tank, estimated that "between 50-100 civilians had perished from air strikes in the six months of the campaign". But, it added the caveat that the "figures [for civilian casualties] vary wildly".
Twelve years after Nato's bombing campaign over Kosovo, there is still no accurate figure for the number of civilians killed. The estimates are between 200 and 500.
It is likely that, in Libya, most civilian casaulties were caused by fighting on the ground between pro-Gaddafi and rebel forces.
There have already been well-documented reports of revenge killings by both sides.
Nato says it has no teams on the ground to assess the impact of its air strikes on the civilian population.
It has been left to organisations such as Amnesty International and Human Rights Watch to try to establish the scale of the killing - including examining the effects of Nato's air strikes.
But it might take years to get a picture of what really happened. And, even then the figures are likely be open to dispute.