Editor's note: CNN's Ivan Watson and crew are some of the few international reporters in Syria, whose government has been restricting access on foreign journalists and refusing many of them entry. Check out more from CNN inside Syria.
Rebel-controlled northern Syria (CNN) -- Mohamed Rashid walked out of the gate of his house with a giant blood stain on his white T-shirt.
"This is the blood of a martyr! Of a hero! Of a lion!" he bellowed. "This is his blood. It is pure!"
Mad with grief, Rashid kissed his bloody T-shirt before being led away by worried relatives.
Just hours before, Rashid learned his son Abdul was killed in battle in the Syrian city of Aleppo.
Housam Abdul Rashid was a 22-year-old defector from the army. He was also the fourth man from his small hilltop village to be killed fighting for the rebels.
The younger Rashid is one of the casualties of the five-day-old rebel offensive on Aleppo, the country's commercial capital. Another rebel, who asked only to be named "Khorshid" because his wife and children were still living in Aleppo, described how his comrade was killed by a helicopter gunship, while climbing onto a rooftop.
"Housam's specialty was a sniper," Khorshid said. "He went to the roof, and a helicopter gunship killed him. Another fighter from Aleppo with him was also killed. I was just 4 meters away when it happened."
Khorshid said the rebels mounted their offensive on Aleppo last Friday, two days after a bomb killed four of Syria's top security officials.
Rebel commanders and fighters claimed they made gains, particularly in the neighborhood of Salahuddin. But they were also clearly suffering casualties.
What began 17 months ago as a peaceful protest movement has evolved into a full-fledged armed insurgency.
Countless rebel battalions with names like "Shield of Idlib Battalion" and "Freedom Brigade" have emerged, as well as military rebel councils in large towns and cities.
The rebel militias are composed in large part of defector soldiers. But there are also many civilians, including students, shopkeepers, real-estate agents, and even members of President Bashar al-Assad's ruling Ba'ath party.
Ahmed Habib spent a decade working as a bureaucrat with the Aleppo branch of the Ba'ath party. But eight months after joining the rebels, he was now dressed in improvised military fatigues, carrying a Belgian-made Fabrique Nationale assault rifle slung over his shoulder.
"We wished to have a new democracy when Bashar al-Assad became president," he said, when asked about his years of Ba'ath party service.
"We wished to have freedom for the people, but that never happened. We just got new cars and computers. It's ... nothing," he cursed in English.
"We tell Bashar al-Assad, very soon we will be in Damascus, in the president's palace, we promise that," Habib said. "He has to hear that and he has to leave, otherwise we will kill him."
Habib was now bivouacked in a village school in Syria's Idlib province which had been converted into a barracks for rebels from the Syrian Falcons Brigade.
The group's leader, Mustafa Abdullah, claimed to lead 600 men. Though he insisted all of his fighters were Syrians, at least one armed man introduced himself to CNN as a citizen of Turkey. Fighters were heard telling the Turk not to speak to journalists in Turkish.
Meanwhile, residents of the village where the Syrian Falcons were headquartered said there were fighters of several North African nationalities also serving with the brigade's ranks.
A volunteer Libyan fighter has also told CNN he intends to travel from Turkey to Syria within days to add a "platoon" of Libyan fighters to armed movement.
Though there are some foreign volunteers, it is clear the bulk of the fighters are Syrians. Every day, it appears there are new volunteers.
One of the newest recruits is Soukrot Amin, a 23-year-old native of Aleppo, who was determined to start his own rebel group.
Amin smuggled himself across the Turkish border to Syria on Sunday, carrying a bag full of walkie-talkies, sniper scopes and novelty spy cameras disguised as watches and car keys -- all tools for his rebel cell.
He said he bought the devices with savings earned after spending five months working as a car mechanic in the United Arab Emirates.
"I go to war for my family, for my country," Amin said. "Because (Assad) has killed everyone. He killed my cousin. He destroyed my village. He destroyed my home."
The young volunteer said he had a list of around 40 recruits for his group. He said he had only 15 weapons for his group. But Amin added that upon arrival in Aleppo, he planned to apply to a group in Turkey calling itself the High Revolutionary Council for weapons to arm his fighters.
"We will win," Amin said.
The veteran fighter named Khorshid had no illusions that the fight for Aleppo would be easy.
He choked back tears after burying his slain friend Housam Abdul Rashid on Tuesday.
But then he swore to return to the battle in Aleppo, within a matter of hours.
"Tonight," Khorshid said. "We must fight Bashar al-Assad, because if not, he will kill us."