Mannagh, Syria (CNN) -- Here in the north, rebels call it "the final battle." For more than a month, lightly armed fighters have hurled themselves against a well-fortified helicopter base located less than a 15-minute drive from the border with Turkey.
The rebels say the last piece of government-controlled territory between Turkey and Syria's largest city, Aleppo, is Mannagh airbase. The battle for it is a modern-day siege.
"It is like a germ infecting the countryside. If the regime has even a 1% chance of taking back this region, this is a base that they would then want to rule from," said Abu Marwan, the young commander of the rebel Northern Storm brigade. "Once it has been captured, the north will be liberated."
But it is not clear how long the final battle for Mannagh airbase will ultimately take.
The siege does underscore one important point: It has taken less than a year for Syria's rebels to go from being hunted in their homes to now encircling and attacking some of the largest military bases in the country.
If and when this airbase falls, the rebels will be able to declare themselves the undisputed rulers of the north.
Spying from the olive groves
The fighting around Mannagh has devastated the farms and villages that dot this verdant corner of Syria.
Intermittent gunfire crackles across the countryside. Periodically, artillery from inside the base unleashes devastating cannon fire that sends up plumes of smoke and dust from shattered, deserted villages around the installation.
"The day the airport falls will be a holiday," said a farmer who asked only to be called Abu Yashar, to protect himself from retribution. Abu Yashar long ago sent his family away for safety and was one of the only civilians seen during a recent visit to the battle zone. His house was located about five kilometers, or three miles, from the airbase, where machine guns could be heard rattling for more than an hour.
Abu Yashar pointed out small bomb craters in his surrounding fields and displayed an unexploded mortar round that landed on his property. He also showed where artillery shells from the airbase slammed into his tractor and into a concrete shed.
"Everything the people need to survive is being targeted by the regime," the farmer said.
The airbase itself is a sprawling walled compound located not too far off a main road.
From amid the cover of tidy rows of olive trees that surround the installation, one can see with the naked eye at least three helicopters parked on the tarmac.
It was here in the olive groves that Abu Marwan and another commander named Abu Jelan had set up a telescope to spy on their enemy.
"The soldiers have started moving from inside the restaurant," Abu Jelan announced into a walkie-talkie, as he peered through the scope. He tried to call in sniper fire. "Guys, snipers! They're moving from the clubhouse to the west. They're running."
The two commanders were helping a rebel mortar team at another location target their attacks on the base.
Before every round of mortar fire, the fighters murmured a little prayer to each other over their radios.
After thunderous explosions, they tried to assess the impact of their attack.
"It landed 10 meters short of the wall," a man on the radio said after one mortar attack.
Another mortar misfired and could be heard spinning out of control and landing far short of the base.
Disappointed, Abu Marwan explained the rebels were trying to use homemade artillery rounds. But then he proudly displayed an enormous, 30-foot-long cannon his men had captured from the Syrian military.
"We will use their own weapons against them," he said, pointing to a plate engraved with Syrian military logos, fixed to the base of the cannon.
Sizing up the siege
Though the rebels appear to have trapped the government troops, they have also suffered losses.
At least two top commanders in the Northern Storm Brigade have been wounded. Their loss has propelled Abu Marwan, a surprisingly shy pilot in his 20s who defected from the Syrian military more than a year ago, into a top leadership position.
"I may be the youngest fighter in the group," the former lieutenant said with a smile, after declining to reveal his exact age.
Videos secretly filmed by opposition activists show Syrian soldiers almost casually walking around tanks and tents in the airbase.
Last Sunday, rebels said the defenders broke through the siege lines to receive a much-needed delivery of supplies under cover of darkness. First, warplanes roared overhead, they said, sending people running for cover. It was then that a helicopter flew in, picked up wounded soldiers, and dropped off supplies before leaving.
A special forces soldier who escaped from the base and surrendered to rebels last week told CNN the troops inside were segregated between mostly Sunni Muslim foot soldiers like himself and officers who were predominantly Alawite, the same religious minority as Syrian president Bashar al-Assad.
"They discriminate between the Alawites and Sunnis," said the soldier, a 22-year-old man from the southern city of Deraa, who asked not to be named.
"The Sunnis go to the front almost as if they are human shields ... and all the Alawites stay behind."
The soldier said there were large stores of food and even supplies of electricity for commanders.
As for weapons, "we have so many weapons at the airport I can't even count. But despite that I could (see) that (the rebels) are not afraid."
The siege forces appear to have received fresh reinforcements in past weeks.
Last weekend, a CNN team of journalists traveled towards the front lines escorted by a young activist from an opposition media center in the nearby anti-regime town of Azaz.
Shortly after passing a line of bombed out buses and trucks serving as a barricade, the reporters were intercepted by a small group of fighters, who covered their faces once they spotted cameras.
"I am very sorry that you traveled all this way, but you have to leave," their hooded leader explained politely, yet firmly, in fluent English. "This is a restricted military zone."
The guide from the Azaz Media Center later explained that the fighters were members of an Islamist rebel group affiliated with the Muslim Brotherhood. He said another group of fighters spotted around several parked pickup trucks were members of al-Nusra Front.
Last month the U.S. government blacklisted al-Nusra, declaring it a terrorist organization linked to al Qaeda. However, al-Nusra rebels continue racking up victories on the battlefield and appear to be attracting growing respect from many supporters of Syria's weary armed opposition.
Streaming out of Syria
Syrians and foreigners continue to flee the fighting.
Nearly 5,900 refugees entered neighboring Jordan over the previous 24 hours, the kingdom's state-run news agency, Petra, reported Tuesday. Border guards gave the refugees humanitarian aid and took them to Zaatari refugee camp.
Russia was planning to fly out about 80 of its nationals who have managed to leave Syria, government officials said, according to RIA Novosti. Two planes arrived in Beirut from Moscow to evacuate the Russian nationals, who have made their way to Lebanon.
"The group includes Russian women who have married Syrians, their children and husbands who have acquired Russian citizenship," RIA Novosti said, adding they will be flown to Moscow.
At least 51 people died in the civil warfare on Tuesday, the opposition Local Coordination Committees of Syria said.
CNN's Salma Abdelaziz contributed to this report