South Australia was the only British colony in Australia which was not a convict colony. It was established as a planned free colony, and began on 28 December 1836. As such, garrisons were not required as prison guards, unlike the other colonies. However, Governor John Hindmarsh was escorted on by a contingent of nineteen Royal Marines. They were assigned to protect him and left South Australia when he departed the colony on on 14 July 1838. A lack of any form of defence however, led to the creation of the Royal South Australian Volunteer Militia, consisting of an infantry company and two cavalry troops, in 1840, although it was disbanded in 1851; for the final six years of its existence it had been a force that had existed on paper only. The first artillery pieces arrived in South Australia aboard "Buffalo", which landed two 18-pounder cannons, but initially there were no moves to form an artillery unit, so the guns were operated by Royal Engineers. In 1844 a request for further pieces was sent to the British government and two years later two light 6-pounders, two 12-pounder howitzers and two Cohorn mortars arrived with an ammunition store of about 500 rounds for each weapon type.