This chapter highlights the implications of Second Gulf War for Israeli defence doctrine. During the years following the war, various ideas on defence lessons were voiced in Israel from time to time, but it is doubtful whether a methodical analysis or comprehensive and systematic formulation of these notions was set forth or, at least, none reached learned observers. The Second Gulf War was not simply a fleeting episode in the history of the region, but was rather a traumatic event and an important watershed, both militarily and politically. The Second Gulf War illustrates a classical case of a war of choice. In this war the US went to battle without there having been any threat to its survival or serious danger to its security. Several remarks are in order on a traditional and universal principle of the doctrine of war and defence especially since the Lebanese War namely, a war of choice or preventative war.