In Australia, new provinces were founded with Victoria in 1835 and South Australia in 1842. The focus shifted from transportation of criminals to voluntary immigration. New Zealand became a British colony in 1839; in 1840 Maori chiefs ceded sovereignty to Britain in Treaty of Waitangi. In 1841 New Zealand became an autonomous colony. The signing of the Treaty of Nanking in 1842 ended the First Opium War and gave Britain control over Hong Kong Island. However, a disastrous retreat from Kabul in the same year led to the annihilation of a British army column in Afghanistan. In 1845, the Great Famine began to cause mass starvation, disease and death in Ireland, sparking large-scale emigration. To allow more cheap food into Ireland, the Peel government repealed the Corn Laws. Peel was replaced by the Whig ministry of Lord John Russell.