Book excerpt: This is a case study of possibly the most complex defensive system in Australia between 1803 and 1945. Defending Victoria was such a wide ranging and demanding task that the colony, and later the state, of Victoria was known as the Gibraltar of the South. This book fills a major gap in Australian military and naval history. Using Victoria as a case study, the book shows how defence developed from the idea of a basic sand fort emanating from a fear of French invasion during the early 19th century, into a complex, modern three-dimensional defensive system incorporating air, land and sea defences as well as radar and secret defence technology by the 1940s. The book is not a simple narration of facts and events, but a substantial addition to Australian military history, on account of its extensive analysis of the political, social, economic and technological factors which impacted defence over many decades of the 19th century.