Complex sentence: Australians received the George Cross under the Imperial Honours System until the establishment of the Australian Honours System, when the new but equivalent award known as the Cross of Valour was created by letters patent within the Commonwealth of Australia and its Territories on 14 February 1975.
Split into simpler sentences: Australians received the George Cross under the Imperial Honours System until the establishment of the Australian Honours System in 1975. The George Cross was replaced by the new award, the Cross of Valour, which was created by letters patent within the Commonwealth of Australia and its Territories on 14 February 1975.