The FMLN's victory came after 17 years out of power
By Stephen Gibbs
Central America correspondent, BBC News
Historians attempting to write a definitive history of how the the Cold War ended need to leave plenty of space for some unexpected appendices.
Take what happened on Sunday night in El Salvador.
The Farabundo Marti National Liberation Front (FMLN), once targeted by the US government as a threat to the world as we knew it, whose defeat was seen as being worth billions of dollars and thousands of lives, gains power.
The young revolutionary leaders who once attracted the attention of the Kremlin or the CIA are now middle-aged men
The US administration sends its congratulations, and says it "looks forward to working with the new government".
The man who will finally bring the party of former Marxist guerrillas from the jungle to the presidential palace is not perhaps the person the Pentagon analysts of the 1980s expected.
Mauricio Funes has never been seen in army fatigues, or carrying an AK-47. He likes a grey suit and designer spectacles. His weapon of choice is a natural eloquence, and a glowing CV from his former employer - CNN.
His view of the American administration is yet more evidence of how the world, and the White House, has changed.
Mr Funes is an admirer of President Barack Obama. He even used his image in his election campaign - something the local US embassy thought was taking things too far.
The FMLN's journey from guerrilla army to government has many parallels to the voyage made by another group of (confusingly similarly abbreviated) left-wing rebels, in neighbouring Nicaragua.
Mr Funes's opponents say he is a puppet of Hugo Chavez
The FSLN, or Sandinista National Liberation Front, took power in 1979, establishing a revolutionary government.
Throughout the 1980s the Reagan administration, fearing communism in its back yard, poured money and weapons into the hands of the group's opponents, collectively called the Contras, to try to unseat the rebels.
Finally, the Sandinistas were voted out of power in 1990.
But fast-forward to 2006, and they are back. The group's historic and once-feared leader, Daniel Ortega, is president of Nicaragua.
He undoubtedly remains an irritation to plenty in the US government and elsewhere, who still question his commitment to democracy. Yet it is hard to imagine President Obama spending much of his time worrying about Mr Ortega, as President Reagan once did.
New Cold War?
Plenty has changed. The young revolutionary leaders who once attracted the attention of the Kremlin or the CIA are now middle aged men.
If age has not tempered their radicalism, years in opposition have done so.
Since it was established as a legal political party, El Salvador's FMLN has spent 17 lonely years out of power, watching three of its candidates for president be soundly defeated by the conservative Arena party.
The radicals were left almost voiceless as El Salvador became the most steadfast ally of the US in Latin America.
They stood by as Salvadorean troops were sent to Iraq, and the US embargo on Cuba - where many FMLN guerrillas had trained - was not opposed.
Those years led the the party to rethink its strategy, and drove it to Mauricio Funes.
Some suggest that he is a front man, and point to the the fact that his running mate is Salvador Sanchez, a former guerrilla commander.
Others suggest that a new Cold War in Latin America is beginning, only with different protagonists: Venezuela's Hugo Chavez cast as the new Khrushchev, gathering acolytes into his fold.
With the economic crisis putting real pressure on the economies and people of Latin America, there will be plenty of opportunity for division and radicalism.
But look at Mr Funes, and it is tempting to believe that the real war is over.