Enterprise CV-6 in Fleet Problem XX
Enterprise CV-6 and an accompanying destroyer in Fleet Problem XX, 13-26 February 1939. During the exercise, Enterprise was "sunk" by another carrier, Ranger CV-4, after that carrier located Enterprise via High Frequency Direction Finding (HFDF) equipment and launched a surprise "attack". This demonstration added weight to the evolving doctrine that in a carrier-vs-carrier conflict, the side that struck first would prevail.