Answer:
In the metaphors “move forward into broad, sunlit uplands” and “sink into the abyss of a new Dark Age” Churchill is most likely referencing the idea that this war could either make or break the world. In this idea, the making of the world is described by the metaphor “move forward into broad, sunlit uplands” which is evident by the phrases “moving forward”, and “broad, sunlit” and their positive connotations. On the other hand, the breaking of the world is described by the metaphor “sink into the abyss of a new dark age”, evident because of the phrases “sink”, “abyss”, and “dark age”. This would fulfill Churchill’s purpose of persuading the British people because he is basically explaining that the result of the war could either involve the country’s success or the country’s downfall, which emphasizes the severity of the situation.