 Complete the following phrase:  In 1892 Clarke published Fortification: Its Past Achievement, Recent Development and Future Progress. The book was influential in shaping the British view of military fortification. Clarke adhered to the Blue Water school of thought which saw the Royal Navy as Britains primary defence against invasion. Large scale permanent fortifications built in peacetime such as the Palmerston Forts were seen as a waste of money. Instead Clarke advocated the use of small field fortifications which could be built cheaply and rapidly, such as those based on the Twydall Profile. His view was based in part on the successful 