The FARC secretariat at the opening ceremony of the 10th FARC conference in the Savannas of Yari in Colombia. (João Pina for The Washington Post)

— Of all the strange sights at the “conference” held this week to mark the end of the FARC guerrillas’ half-century war, none was more surreal than the concert stage they fired up in the evenings. Set in the middle of a vast meadow, with a fog machine and a video screen the size of a tank, it was the brightest thing for miles around.

Big-name bands had been trucked in from the faraway capital, Bogota, and some of the rebels came out of the forest to dance in their fatigues and rubber boots. Others stared blankly, looking bewildered by all the light and noise.

“I went to watch for a bit, but it hurt my ears,” said David Preciado, 33, who had never been to a concert. He has been fighting in the jungle since age 14. “I guess I’m not used to it,” he said.

No one — not the guerrillas and certainly not the Colombian public watching them — is used to any of this.

The Revolutionary Armed Forces of Colombia, or FARC, has reached a peace deal with the government that, if approved by voters Oct. 2, will bring an end to the longest armed insurgency in the Western Hemisphere.

To prepare, FARC leaders gathered 200 guerrilla “delegates” this week for a six-day conference with the stated purpose of discussing the accords and smoothing the rebels’ transition to electoral politics.

Clearly the rebel commanders also wanted to throw their troops a party, and the result was something like a Marxist-Leninist version of a USO show.

During the day, while the commanders and delegates met behind closed doors, hundreds of rank-and-file guerrillas who had been brought in to provide security and other assistance played soccer, cooked elaborate stews and patiently attended to the questions of the many Colombian and foreign journalists invited to the event. At night, the beer flowed and booming music rattled the jungle.

The conference was held five hours from the nearest town, in an area of eastern Colombia known as the Savannas of Yari, a name that once conjured fear. It is where the FARC often kept those it kidnapped, chained in the jungle, and where others vanished forever.

This week it became the setting for an impromptu rebel city, with generators pumping 24-hour electricity, restaurant tents offering Old Parr whisky and cold beer, and nightly concerts under a full moon. Vendors selling T-shirts, ice cream and hamburgers showed up, too. It felt like a hybrid of Burning Man and a communist summer camp, only with AK-47s instead of Frisbees.

David Preciado lost his left arm in combat six years ago. (João Pina for The Washington Post)

A few family members also arrived to reunite with loved ones they haven’t seen in years. If the peace deal is approved, FARC troops will begin relocating to U.N.-monitored camps where they will start disarming, and their relatives are expected to be able to join them.

Preciado, who lost his left arm in combat six years ago, hasn’t seen his parents or siblings since 1997, when he joined the guerrillas. They have no idea whether he is alive, he said. Preciado has sent friends to check on them without their knowledge.

He let out a heavy sigh when asked what it would be like to meet them again. “A sea of tears,” he said.

Fight moves to the ballot box

The latest polls show the Oct. 2 referendum measure is likely to pass by a wide margin. But it was difficult to tell how the guerrillas’ celebratory event might play on television to a Colombian public still conflicted about the deal, which would allow FARC leaders to avoid prison time if they fully admit to war crimes and make amends.

There appears to be even more resentment, at least among poorer Colombians, that the deal would give demobilized fighters cash stipends to facilitate their transformation to civilian life. FARC commanders have insisted the organization has no money to contribute, despite the widespread perception that the rebels have socked away hundreds of millions of dollars from drug trafficking.

The infrastructure set up for this week’s event — heavy construction equipment, a gas station and especially the concert stage — probably cost the FARC hundreds of thousands of dollars.

FARC commanders were evasive all week about their plans, ducking most reporters’ questions. The peace accords commit the Colombian government to dedicating more money and attention to rural development, but the pact does not promise the kind of sweeping economic and political change that has long been at the core of FARC revolutionary doctrine. The group says it will fight for those ideals at the ballot box.

The FARC, or at least the still-unnamed party that will succeed it, will enter electoral politics at a time when the left is losing ground across Latin America. In speeches, there was much praise for Venezuelan leader Hugo Chávez, who died in 2013, but little indication the guerrillas view his “Bolivarian” socialist movement as a guidepost.

Pablo Catatumbo, a member of the seven-man FARC leadership secretariat whose real name is Jorge Torres, said their movement would be devoted to “fighting corruption,” with a deep respect for opposing views and ideas.

“We will maintain the principles we’ve always been struggling for: a Colombia that is more inclusive, more fair and that respects democratic freedoms,” he told reporters.

Out in force

It was here on the Savannas of Yari that the Colombian government held failed peace talks with the rebels from 1999 to 2002. The FARC was at the height of its power then, with as many as 20,000 fighters.

FARC guerrilla fighters attending the opening ceremony of the FARC conference. (João Pina for The Washington Post)

The government says the rebel force has withered to fewer than 7,000 combatants, but the true number remains a closely guarded FARC secret. For those accustomed to seeing photographs of smaller rebel units, it was impressive to see hundreds of battle-hardened, disciplined fighters in one place. Although diminished, they remain the last major guerrilla army in the Americas, and there is little doubt they will be able to keep fighting if Colombian voters reject the peace accords.

No one here seemed to be contemplating that scenario. But Colombian opposition leaders from the party of former president and FARC archenemy Álvaro Uribe arrived to campaign against the accords this week in San Vicente del Caguan, the town closest to the site of the conference.

The town’s mayor, Humberto Sánchez, was kidnapped by the rebels in 2006 and was held six months in the forest until his family paid a ransom, he said.

Sánchez said local businesses were forced to make extortion payments to the guerrillas until a month ago, and he predicted many in town would vote against the accords. “A badly negotiated peace deal is worse than war,” Sánchez said.

Asked what they plan to do after giving up their weapons, a few rebel fighters at the conference said they wanted to go back to school or return to farm life. All said they were ready to do whatever their commanders asked of them.

“I’d really like to work in media,” said Adriana Gutierrez, 32, after meeting so many reporters this week. “This work seems really important right now.”

Gutierrez was getting ready for an interview with a BBC cameraman. She has been living in the jungle as a guerrilla soldier since age 17.