The correct answer is SHIFT.
In this excerpt, Churchill moves (or shifts) from speaking about the first four years of the last war (which were filled with "disaster and disappointment") to speaking about the morale of the Allies (which was high despite disappointment).
Churchill is not using understatement, which is describing something as smaller than it really is here. He is also not using logos, because he is not providing a logical argument to explain why the Allies would have such high morale despite disappointment. Finally, he is not using parallelism, because these ideas are all phrased differently.