Colombian President Juan Manuel Santos has hailed the death of Farc leader Alfonso Cano as the greatest blow against the left-wing guerrilla group.
Mr Santos also said the choice faced by the rebels was to demobilise, go to jail, or face an early grave.
He was speaking after travelling to the camp in Colombia's south-west where Cano was killed by the army on Friday.
Meanwhile the Farc reportedly vowed to continue their decades-long struggle despite the death of their leader.
The pledge was made on the Swedish-based Anncol website, which has often carried statements by the Revolutionary Armed Forces of Colombia (Farc) in the past.
President Santos was speaking on Saturday at an army barracks in Popayan, the capital of Cauca province, near the camp where Cano was shot dead during a battle with security forces.
"It is the most devastating blow this group has suffered in its history," he said, adding that the operation had been long in the planning.
He said news of the death of Alfonso Cano, whose real name was Guillermo Leon Saenz, would change Colombia's history for the better.
And the president revealed that intelligence had been gathered "from a number of sources".
"And with the collaboration of people within the Farc, our armed forces slowly planned the operation they carried out yesterday."
Military officials said the operation was continuing, with 17 helicopters patrolling the area around the camp.
Mr Santos also sent a warning to all Farc members: "I want to send a message to each and every member of that organisation: 'Demobilise'... or otherwise you will end up in a prison or in a tomb. We will achieve peace".
But he also urged the armed forces not to feel triumphalist, but to persevere in their battle against the rebel group.
Beard shaved off
On Friday morning, the Colombian Air Force started bombing the camp where Alfonso Cano was believed to be hiding. Later that day, special operations forces moved in.
They found items belonging to Cano, as well as computers, memory sticks, hard discs and $100,000 in cash.
They surrounded Cano and his men and, according to Defence Minister Juan Carlos Pinzon, killed him in the firefight which ensued.
The defence ministry released pictures of the dead leader, with his trademark bushy beard shaved off.
Security forces have killed a number of Farc commanders and arrested many others in recent years. In September 2010, Mono Jojoy, another top Farc commander, was killed in a bombing raid.
The military has been able to expand its operations against the rebels with the help of the US, which has provided billions of dollars in funding, training and intelligence-sharing.
The Farc is on US and European lists of terrorist organisations.
Colombia's civil conflict has lasted more than four decades, drawing in left-wing rebels and right-wing paramilitaries.