Complex sentence: The British-Indian survivors eventually made it to British-held Kandahar--the city was later besieged by the Afghan rebels until a relief force, led by Major-General Roberts, arrived from the capital city Kabul in September.
Split into simpler sentences: The British-Indian survivors eventually made it to British-held Kandahar. The city was later besieged by Afghan rebels until a relief force, led by Major-General Roberts, arrived from the capital city Kabul in September.