By Jeremy McDermott
BBC News, Bogota
Farc loses arms and ammunition in raids, but is far from defeat
The Revolutionary Armed Forces of Colombia (Farc) are celebrating their 45th anniversary, making them one of the oldest insurgent forces in the world - and, despite recent setbacks, still one of the strongest.
"The Farc are at their worst point in 45 years of fighting," said Alfredo Rangel, head of the Bogota think-tank Security and Democracy.
"Up until recently they had always been growing, in numbers and territory. Now they are being driven back, and their numbers are falling. They are in terminal decline."
Yet while the Tamil Tigers, one of the most brutal and innovative insurgencies, are crushed and the Nepalese Maoists opt for the political route (at least for the moment), the Farc remain committed to their increasingly improbable aim of overthrowing the state and imposing a socialist regime.
Its members are motivated neither by religion or ethnicity. The Farc are a throwback to the 1960s, when Cuban-inspired insurgent groups sprang up in South and then Central America.
And they are pretty much all that remain of those insurgencies that swept through Latin America.
They have recently taken a battering, reduced from almost 16,000 fighters in 2002 to half that today, with a record 3,000 deserting ranks in 2008.
Last year their founder and legendary leader, Manuel "Sureshot" Marulanda, died of a heart attack aged 78.
Two other members of the Farc's ruling body, the Secretariat, were killed, one in an aerial bombardment of a rebel camp in neighbouring Ecuador, another murdered by his own bodyguard, who cut off a hand to show the authorities and claim a reward.
The Farc leader, known as Alfonso Cano, has launched "Plan Rebirth".
Yet the Farc are far from defeated. They have new leaders, including a bespectacled and bearded anthropologist known by the alias Alfonso Cano, long the movement's ideologue, a committed Marxist Leninist and hardliner.
He has now established his control over the movement, since the death last March of Marulanda, and delivered his new strategy for the rebels, called Plan Rebirth.
The Farc have stepped up their campaign, with more attacks so far this year than any year since 2003.
And the rebels are trying to move away from their peasant roots and project themselves into Colombia's cities, aided by training from international groups like the Provisional IRA and the Basque separatist group Eta.
The Farc's communique celebrating their 45th anniversary was defiant and optimistic.
"The decisive stage of the fight for peace has begun," read the message posted on the internet. "We have sworn to win and win we will."
Much of the Farc's longevity, certainly since the mid-1980s, can be attributed to one thing: cocaine.
Whilst the Farc are ultra conservative in their doctrine and tactics, they have proven themselves to be adept businessmen, latching onto the drugs trade and taking their cut from all the links in the narcotics chain, from the coca fields up to the vacuum-packed bricks of cocaine that leave Colombia's shores at a rate of over 600 tonnes a year.
According to Roman Ortiz, security expert at the Ideas for Peace Foundation, the drugs trade has provided more than just overflowing coffers.
"The Farc have also inherited a support base from their involvement in the drugs trade," said Mr Ortiz. "They get support and recruits from the peasants who cultivate and harvest the drug crops."
Out of reach
The Farc have two other crucial advantages which they maximise: topography perfectly suited to guerrilla warfare, and long borders with nations not interested in, or unable to crack down on, rebel activity.
Colombia could not have been designed any better for an insurgent force. It has three mountains ranges that trisect the country and the lower levels are coated in dense jungle.
Like the Taliban in Pakistan and the Vietcong in Cambodia, the Farc use the border regions, mostly impenetrable jungle, to rest and recuperate, plan attacks and get supplies and weapons, all out of reach of the Colombian security forces.
Intelligence sources indicate that four members of the Secretariat now reside outside Colombia.
There have long been accusations, vehemently denied, that President Hugo Chavez of Venezuela sympathises with the Farc.
What is clear is that the Farc have camps on Venezuelan soil and many of their supplies come from here and from Ecuador.
The latter uses the US dollar as its currency, meaning that the dollars that come into rebel coffers from the US drugs market can be readily translated into food, medical supplies, uniforms and black-market arms and munitions.
"We have incontrovertible evidence that elements of the Venezuelan military not only turn a blind eye to Farc presence on their soil, but actively help them with weapons and logistics," said a senior intelligence figure in the Colombian defence ministry. "As long as this continues, our chances of a military victory are slim."
Leaner and meaner
Other borders are with Panama, which has no army; Peru, still unable to defeat the remnants of its own rebel force, the Shining Path; and Brazil, whose border sweeps into the Amazon basin, where visibility is reduced to a few metres amid the triple-canopy jungle.
And under orders to recruit quality not quantity, the Farc are becoming leaner and meaner.
The money from drugs continues, whereas the tax revenues the state needs to keep the US-backed military machine on the offensive are shrinking thanks to the world financial crisis.
President Alvaro Uribe, who may well stand for a third term in office, assuming he can change the constitution once again, has shown no desire to negotiate with the rebels, who killed his father in a botched kidnap attempt.
The Farc celebrate their 45th anniversary secure in the knowledge that it will not be their last.