BEIRUT, Lebanon - As Syria's conflict enters its fourth year, ravaging the country and creating a massive humanitarian crisis, President Bashar al-Assad's regime is on the offensive to regain territory from a divided opposition.
Diplomatic efforts by Russia and the United States are all but on hold with the two powers now divided over the crisis in Ukraine, while the fighting continues on the ground in Syria.
"Without Western intervention, the war will continue for many years more and such an intervention is very unlikely while (US President Barack) Obama is in the White House," said Thomas Pierret, a Syria specialist at the University of Edinburgh.
"Things could change after 2016", after elections to choose Obama's successor, he said.
For now, neither side seems to have the means to win decisively a conflict that has cost more than 140,000 lives and displaced nearly half of Syria's population, many of them now refugees.
The conflict began in March 2011, with peaceful anti-government protests that were brutally repressed.
The opposition took up arms, and the insurrection developed into a full-blown war by February 2012 with the regime's bombardment of central Homs.
After watching its territory shrink, the regime launched a counter-offensive in the spring of last year, shored up by Lebanon's Shiite Hezbollah and Iraqi Shiite fighters trained by Iran's Revolutionary Guards.
It was bolstered by having avoided threatened Western military action in the wake of a deadly chemical weapons attack in August 2013 that activists blamed on the government.
And its strategy now has become to protect "useful Syria": The coast, the major towns of the north and south and key roads.
The opposition now controls more territory than the regime, but the regime controls the more densely populated regions of the country.
It is advancing on three fronts, south of the capital Damascus, in the strategic Qalamun region near the Lebanese border, and in the city of Aleppo in the country's north.
Near the capital, it has negotiated limited ceasefires with neighbourhoods under army sieges, where populations have suffered from dwindling food and medical supplies.
In Qalamun, after a string of victories last year it has encircled Yabrud, the last rebel stronghold in the region.
And in Aleppo, it has retained its grip on the western side of the city, while advancing around the outskirts of the rebel-held east as well as securing and reopening the nearby airport.
'No good scenarios'
At the same time, the opposition is more divided than ever, fighting both the regime and its former ally, the jihadist Islamic State of Iraq and the Levant (ISIL).
Both moderate and Islamist rebels, and even Al-Qaeda's Syria affiliate Al-Nusra Front, are engaged in the bloody battle against ISIL that began in January and shows no sign of waning.
Despite its recent advances, experts say the regime lacks the manpower to retake all its lost territory.
Experts believe the opposition numbers around 100,000-150,000 fighters, among them between 10,000-20,000 foreign fighters.
There are an estimated 2,000 rebel battalions, with the Islamic Front coalition the most important.
The army numbers some 300,000, half of them conscripts, and can also count on the support of thousands of pro-regime militiamen.
But the regime has suffered heavy losses: 50,000 of its fighters have died in the past three years, the Observatory says.
"Neither side is winning," said Volker Perthes, director of the German Institute for International and Security Affairs.
"Assad could, perhaps, retain the majority of the territory and apply a scorched-earth policy to the areas beyond his control, but he'll never be able to restore all of the country under his regime," he added.
Perthes, the author of Syria Under Bashar, said that the disintegration of the country "is not a possibility, but a reality, and if the war ended tomorrow, it would take more than a decade for the country to recover".
Geographer Fabrice Balanche, whose work focuses on Syria, said a division of the country seemed possible. He predicts "a de-facto partition between the Kurdish region in the north-east, a rebel region in the north and a zone in regime hands in the centre, in the absence of victory by one side or another".
"There are no good scenarios for Syria. Assad will regain control slowly, but at what a price," he said.
"The return of the regime will be accompanied by repression that will encourage hundreds of thousands to stay away," he added.
"And I would be astonished if Syria receives the money that flowed to Lebanon in 2006 (after a conflict with Israel), and the country doesn't have oil like Iraq."