After nearly four years of formal negotiations, the Colombian government is on the brink of finalizing a peace deal with the FARC guerrillas it has been fighting since 1964. The conflict has left more than 220,000 dead and driven nearly seven million Colombians from their homes — the highest number of internally displaced people in the world, according to the United Nations.

A peace deal holds a lot of promise for Colombia, a resource-rich nation of 50 million that is the United States' closest ally in South America. Although the government would still be at war with Colombia’s ELN insurgents, a smaller group — not to mention the drug-trafficking gangs and other warlords who dominate the country’s remote rural areas — no other armed group has the firepower or the hefty symbolism of the FARC, as the Revolutionary Armed Forces of Colombia are known.

A final accord could be signed in coming weeks. But it faces one more major hurdle: voter approval. President Juan Manuel Santos wants a referendum that would give the Colombian public a chance to approve or reject the deal. His powerful archrival, former president Álvaro Uribe, has already started campaigning against it.

Like the Brexit vote, it will be a campaign symbolizing far more — a struggle over Colombia’s future direction and the meaning of its bloody past. Polls indicate a “yes” vote is likely, but many Colombians are unhappy with Santos and think the peace deal lets the FARC off the hook.

It has taken Colombia a long time to get to this point, so here’s a short guide to what’s going on.

I thought the government and the FARC just announced a peace treaty. The war’s not over yet?

Last month, the government and the guerrillas agreed to a bilateral cease-fire and pledged to redouble their efforts to eliminate the last few remaining points of friction. A big one: the terms under which FARC leaders are allowed to enter democratic politics once they return to civilian life. There is a long, dark history in Colombia of the assassination of leftist candidates and legislators, but the Santos government has offered assurances that this time things will be different.

This deal looks like a great thing for Colombia and has a lot of world leaders behind it, including President Obama and Pope Francis. Why would Colombians vote against it? Just to keep the war going?

Santos has staked his legacy on the peace deal. He wants the referendum to present Colombians with a simple choice: war or peace. But his rivals, and especially Uribe, don’t see it that way. They think the deal is a wrist slap for the FARC and a slap in the face to victims of the conflict. And with Colombia’s economy slowing and inflation squeezing many families, it’s not hard for Santos’s opponents to depict the peace deal as a parachute for the guerrillas, particularly as the government takes on the financial burden of rehabilitating some 7,000 FARC fighters who need job retraining, housing, counseling and other services in the transition to civilian life.

From afar, it can be easy to forget that a lot of Colombians view the FARC as simply one more armed group getting rich off the drug trade and other criminal rackets. Conflict and political violence are their status quo. They don’t believe Santos can change that with a piece of paper.

Could the peace deal fall apart?

Unlikely, but it's possible. The referendum — technically a plebiscite —  is now being drafted by Colombia’s highest court. And in order for the peace accord to win the kind of democratic legitimacy Santos is seeking, he’ll want it to pass by a wide margin. If it does not, and it stumbles in the implementation phase, then whoever succeeds Santos as president in 2018 may not see a strong mandate for the accord.

Uribe and his party say they have not decided yet if they will encourage Colombians to cast a blank ballot in protest or to simply vote “no” and reject the deal.

So the FARC could go right back into the mountains and re-arm?

Not likely. Once the final accord is signed, the FARC will gather in 23 “safe zones” and eight camps to begin a six-month phased disarmament under the supervision of U.N. monitors. The plebiscite will probably take place when the rebels are still in possession of most of their weapons. If it results in a rejection of the deal, it’s likely the government and FARC leaders would return to the negotiating table and try to make the terms more palatable to voters. But the rebel camps will be close to their familiar territory, and it wouldn’t be hard for them to return their jungle hideouts if the accord completely breaks down.

That said, seemingly no one in Colombia — not even Uribe supporters — expects that to happen.

If Santos campaigns for the peace deal and Uribe against it, what will the FARC leaders do? Campaign alongside the president?

No. The FARC remains overwhelmingly unpopular with the Colombian public, according to surveys, and the last thing Santos wants is to be seen as some sort of political ally of the guerrillas — even though he is, insofar as he and the FARC both need their deal to stick. Uribe and his supporters will be very much looking to depict it that way.

The government will want FARC commanders to stay quiet and prepare their troops for a post-conflict phase with minimal drama. But FARC leaders clearly view themselves as long-frustrated leftist politicians who took up arms only in self-defense. It seems highly unlikely that they’ll sit on the sidelines while Colombians consider their fate.