Sportsman, author, and conservationist, CLARK C. VAN FLEETis a native Californian who for more than four decades has roamed the forests and fished the streams of the West Coast. Like every true lover of wildlife, he is appalled by the carelessness with which politicians and government officials invade national parks and game sanctuaries which were thought to be inviolate. In the case he is describing, the Pentagon is to blame.