In December, the British marched into Afghanistan and arrested Dost Mohammad, sent him into exile in India and replaced him with the previous ruler, Shah Shuja, who shared their more progressive vision for the people of the region. Shah Shuja ul-Mulk had ascended the throne in 1803 and had signed a mutual defence agreement with the British in 1809 against a possible Franco-Russian invasion of India via Afghanistan. In the same year he was deposed and imprisoned by his half-brother. There were a number of Amirs of Afghanistan until Dost Mohammad Khan gained power in 1836. Shah Shuja was not popular with the Afghans and tensions grew, leading to the killing of the British envoy, Captain Alexander Burnes, in 1841. By January 1842, the Afghans were in full revolt. With a weakening of military discipline, the British decided to withdraw from Kabul. The Kabul garrison of 4,500 troops and 12,000 camp followers left Kabul for Jalalabad that was 80 miles and 5 days march away. They were attacked by 30,000 Afghans. Six British officers escaped on horseback but only one, the wounded Dr William Brydon riding on a wounded horse, made it to Jalalabad. Over one hundred of the British and 2,000 sepoys and camp followers were taken hostage and the rest killed. So perished the "Army of the Indus". In April, a punitive expedition was dispatched and recaptured Kabul and freed the captives in September. The new Governor-General, Lord Ellenborough, decided to withdraw all British garrisons from Afghanistan and Dost Mohammad Khan was freed in India to return to the throne. Dost Mohammad is reported to have said: