Colombian President Juan Manuel Santos and Timoleon "Timochenko" Jimenez, the leader of the FARC rebels, announced a major breakthrough Wednesday in peace talks to end a conflict that has burned for half a century.

Here are profiles of the two men, who met for the first time Wednesday and shook hands at the signing of a landmark deal on bringing justice for crimes committed during the conflict.

- The president -

Juan Manuel Santos, 64, served as defense minister under hawkish president Alvaro Uribe (2002-2010), running a no-holds-barred military campaign against the Revolutionary Armed Forces of Colombia (FARC).

But he switched tack after his 2010 election, launching peace talks with the FARC.

That caused a bitter break with his one-time mentor Uribe, now a senator, who accused him of betraying the nation.

However, Santos staked his presidency on the peace process, winning reelection last year in a vote widely seen as a referendum on the talks.

The center-right leader campaigned on the promise to end a civil war that has killed more than 220,000 people and displaced six million across half a century.

His determination to follow the path of peace appears to be paying off.

After Wednesday's breakthrough deal was signed, Santos vowed to conclude a final peace accord "within six months."

But he is also dogged by the murders of thousands of civilians by soldiers who falsely claimed their "combat kills" were guerrillas.

The scion of a wealthy family entrenched in Colombian politics and the media, he worked in the trade and finance ministries before his stint as defense minister.

He studied at the prestigious London School of Economics and was involved in free-trade negotiations with the United States, Europe and Asia.

- The rebel -

Rodrigo Londono, alias Timoleon Jimenez, alias Timochenko, is the third commander to lead the FARC since the guerrilla group was launched in 1964.

He took over in 2011 after his predecessor, Alfonso Cano, was shot and killed by government forces in an operation ordered by Santos.

Timockenko, 56, was a protege of the FARC's founding commander, Manuel "Sureshot" Marulanda, who led the guerrilla army for more than four decades until his death of a heart attack in 2008.

The young Timochenko grew up in the same coffee-farming region as Marulanda in western Colombia, joining the Communist Youth in the 1970s and studying medicine in the Soviet Union and Cuba -- though he never graduated.

He joined the FARC when he returned to Colombia in 1979 and rose rapidly through the ranks, joining the rebels' top command at age 26.

With his thick salt-and-pepper beard and hefty paunch, Marulanda does not quite fit the image of a guerrilla fighter who lives hiding out in the mountains.

He showed up in Havana Wednesday not in combat fatigues but a black tracksuit.

Timockenko is wanted on charges including terrorism, aggravated homicide and kidnapping.

More than 100 warrants have been issued for his arrest, and he has been sentenced in absentia to more than 150 years in prison.

The United States has a $5-million reward out for his arrest.

Yet Santos's government has now twice tacitly allowed him travel to Cuba to meet with his peace negotiators.

In April 2014, Santos said he would "think twice" before ordering Timockenko killed.