AHC: Land War in the Nullarbor

Your challenge is create and describe the land war between two nations/colonies where one controls OTL Perth and the other controls OTL Adelaide (and farther east as well). The border in the South should be somewhere near the OTL Western Australia - Southern Australia border.
 
...Or the Adelaideans can conquer Perth by ship. (I assume the East Australians are the aggressors, being that they'd be the more populous faction and therefore logically the more powerful.)
 
Top