‘123.’ The opening of "Under the Periscope" sets the stage for the exploits and operations of the British Submarine Service during wartime, highlighting the anticipation and preparations before heading into combat. Readers are introduced to Lieutenant Commander John Raymond and his crew as they prepare for patrol in a dark harbor, discussing their roles and duties while aboard the submarine. The narrative provides a rich tableau of submarine life, characterized by camaraderie, tension, and the ever-present threat of enemy action, all while delving into the technical aspects and the emotional undertones of being part of such a critical military operation. The author implies a mix of factual representations from his own experiences during the war, evoking both the fears and the gallows humor among the crew. (This is an automatically generated summary.)