Photos: Battle for Aleppo Civilians wait to be bussed out of besieged areas of eastern Aleppo, Syria, as evacuations continue on Monday, December 19. A people-swap deal struck between rebels and Syrian government forces was set to begin over the weekend, but evacuations were temporarily put on hold after a number of buses were set on fire. Hide Caption 1 of 35

Photos: Battle for Aleppo Syrian pro-government forces wave to evacuees from the villages of Foua and Kefraya on December 19. While people were being bused out of Aleppo, safe passage was also given to people in areas held or besieged by rebels, the Aleppo Media Center activist group said. Hide Caption 2 of 35

Photos: Battle for Aleppo Militants burned at least five buses assigned to evacuate people in Aleppo on Sunday, December 18. Aleppo has been held by rebels for the past four years, but it is now almost entirely under government control. Hide Caption 3 of 35

Photos: Battle for Aleppo Buses drive through the Syrian government-controlled crossing of Ramoussa, on the southern outskirts of Aleppo, on December 18. Hide Caption 4 of 35

Photos: Battle for Aleppo Russian soldiers and Syrian pro-government forces look on as civilians and rebel fighters are evacuated from Aleppo on Friday, December 16. Evacuations began a day earlier under a new ceasefire between rebels and pro-government forces. Hide Caption 5 of 35

Photos: Battle for Aleppo Pro-government forces guard a convoy of buses and ambulances during the evacuation operation on December 16. Hide Caption 6 of 35

Photos: Battle for Aleppo Civilians arrive in the opposition-controlled Khan al-Aassal region, to the west of Aleppo, on Thursday, December 15. Most of the civilians from Aleppo will be taken to a rebel-controlled area in the neighboring province of Idlib. Hide Caption 7 of 35

Photos: Battle for Aleppo A wounded boy sits inside an ambulance during the evacuations on December 15. Hide Caption 8 of 35

Photos: Battle for Aleppo Staff members of the Syrian Red Crescent wait near ambulances as the evacuation operation gets underway on December 15. Hide Caption 9 of 35

Photos: Battle for Aleppo Buses line up to transport people away from eastern Aleppo on December 15. Hide Caption 10 of 35

Photos: Battle for Aleppo A woman leads family members toward the evacuation buses on December 15. Hide Caption 11 of 35

Photos: Battle for Aleppo A woman in a wheelchair waits to board a bus during evacuations on December 15. Hide Caption 12 of 35

Photos: Battle for Aleppo A member of the civil defense carries a wounded boy out of a hospital in eastern Aleppo on December 15. Hide Caption 13 of 35

Photos: Battle for Aleppo Pro-government forces advance in Aleppo on Wednesday, December 14. Hide Caption 14 of 35

Photos: Battle for Aleppo A wounded woman is helped into the bed of a truck on December 14. Hide Caption 15 of 35

Photos: Battle for Aleppo Buses wait to evacuate people in Aleppo on December 14. Hide Caption 16 of 35

Photos: Battle for Aleppo Pro-government forces advance on December 14. Hide Caption 17 of 35

Photos: Battle for Aleppo Pro-government forces walk in the ancient Umayyad Mosque after capturing the area on Tuesday, December 13. Hide Caption 18 of 35

Photos: Battle for Aleppo Syrians depart a rebel-controlled area of Aleppo on December 13. Hide Caption 19 of 35

Photos: Battle for Aleppo Syrian residents, fleeing violence in the Bustan al-Qasr neighborhood, arrive in Aleppo's Fardos neighborhood on December 13. Hide Caption 20 of 35

Photos: Battle for Aleppo A Syrian child cooks in the street in a rebel-held area of Aleppo on December 13. Hide Caption 21 of 35

Photos: Battle for Aleppo Syrian civilians take food from a storage room that was formerly held by the opposition forces in eastern Aleppo's al-Kalasseh neighborhood on December 13. Hide Caption 22 of 35

Photos: Battle for Aleppo Pro-government fighters wave from a truck as they pass civilians fleeing the Bustan al-Qasr neighborhood on December 13. Hide Caption 23 of 35

Photos: Battle for Aleppo A woman reacts as she evacuates the Bustan al-Qasr neighborhood with her two children on December 13. Hide Caption 24 of 35

Photos: Battle for Aleppo Syrians celebrate in a government-held district of Aleppo on Monday, December 12. Hide Caption 25 of 35

Photos: Battle for Aleppo Pro-government forces patrol the al-Saleheen neighborhood in eastern Aleppo on December 12. Hide Caption 26 of 35

Photos: Battle for Aleppo Rebels in southeastern Aleppo target government forces with anti-aircraft weaponry on December 12. Hide Caption 27 of 35

Photos: Battle for Aleppo Civilians flee the Sukkari neighborhood in southeastern Aleppo on December 12. Hide Caption 28 of 35

Photos: Battle for Aleppo Pro-government forces patrol Aleppo's Sheikh Saeed district on December 12 after it was recaptured from rebel forces. Hide Caption 29 of 35

Photos: Battle for Aleppo In this handout photo from the International Committee for the Red Cross, women displaced from eastern Aleppo gather at a shelter in the village of Jibreen, south of Aleppo, on December 12. Hide Caption 30 of 35

Photos: Battle for Aleppo Smoke rises from the Bustan al-Qasr neighborhood on December 12. Hide Caption 31 of 35

Photos: Battle for Aleppo Civilians from eastern Aleppo stream into a government checkpoint at the al-Hawoz street roundabout on Saturday, December 10. Hide Caption 32 of 35

Photos: Battle for Aleppo Rebel fighters take aim at pro-government positions in Aleppo on Friday, December 9. Hide Caption 33 of 35

Photos: Battle for Aleppo Syrian rebels walk down a street in eastern Aleppo on December 9. Hide Caption 34 of 35