As a two-month-old cease-fire collapses and peace talks stall, the northern city of Aleppo is once again a main battlefield in Syria's devastating civil war. More than 60 people have been killed in less than 24 hours in airstrikes and shelling on contested neighborhoods of the city.
A look at Aleppo:
Syria's largest city and once its commercial center, Aleppo was a crossroads of civilization for millennia. It has been occupied by the Greeks, Byzantines and multiple Islamic dynasties. As one of the world's oldest continuously inhabited cities, Aleppo's Old City was added in 1986 to UNESCO's list of World Heritage sites.
But the civil war has damaged its landmarks, including the 11th century Umayyad Mosque, which had a minaret collapse during fighting in 2012, the 13th century citadel and the medieval marketplace, where fire damaged more than 500 shops in its narrow, vaulted passageways. Some historic sites have been used as bases for fighters.
Aleppo was one of the last cities in Syria to join the uprising against President Bashar Assad's government.
Because of its strategic location near the Turkish border and symbolic significance, it is often said that whoever holds Aleppo wins the war. Although it would probably not end the war, should Assad's forces recapture Aleppo, it would mark a turning point in the conflict and deal a devastating blow to the opposition.
Aleppo is about 50 kilometers (30 miles) from the Turkish border, and Ankara enjoys wide influence in northern Syria. Most of the rebels' supplies flow across the Turkish border. If the government succeeds in completely blockading the city, it would choke off the rebels and potentially force their surrender. It would also be catastrophic for tens of thousands of civilians still living there.
A DIVIDED CITY
A number of insurgent groups control several neighborhoods of the city, which has been rocked by airstrikes and is being attacked from the west, south and east by government forces. The only rebel supply line is a corridor that links the city with northern parts of the province leading to the Turkish border.
Government forces and their allies control most of the eastern neighborhoods as well as the international airport and the nearby Nairab air base.
Militants from the Islamic State group used to control several neighborhoods in Aleppo, but they were forced out by other rebels in early 2014.
The main Kurdish militia, known as the People's Protection Units, or YPG, controls several predominantly Kurdish northern neighborhoods.
The main insurgent groups in the city are the ultraconservative Ahrar al-Sham group; the Nour el-Din Zengi; the Tawhid Brigade; and the Nusra Front, al-Qaida's branch in Syria. Smaller groups also are involved in the fighting.