 Tensions between Britain and the Russian Empire in the 1850s , as starkly demonstrated by the Crimean War , along with Australia @-@ wide moves towards self @-@ government caused a <unk> of the colony 's defence posture . The various colonies regarded themselves as possible targets for the Russian Pacific Fleet , then based in Siberia . In 1854 , Governor Henry Young appointed a commission under Boyle Travers Finniss to report on the defence of the colony , in case of war . Boyle 's report recommended leaving strategic defence in the hands of the Imperial Navy , though South Australia was to purchase a 400 ton naval vessel . Local defence was to be largely handled by the existing small Imperial garrison and local colonial force , supported by the artillery obtained in 1847 . When the Crimean War ended in 1856 , the danger passed and the perceived need for expensive defence preparations with it . For many years nothing substantive came about from debate on defence of the colony . Over time there formed a consensus favouring Semaphore for fixed defences or fortification ; a strategy also argued by the government established Hart Commission in 1858 . Raiders were seen as unlikely to force the <unk> of the Port River but instead were expected to stand off Semaphore , shell the port and use their guns to support landings . The Hart Report recommended building of <unk> towers at Semaphore and Glenelg , the first report to recommend permanent fortification at Semaphore , though none were built mainly due to the cost . 
