What event prompts Smith to investigate her father's war experience?

Zadie Smith had always wanted to dig deeper in her father's war experience, but she never had enough courage to ask him, and neither did he. One day, Zadie finds herself visiting an American poet friend in Normandy. And when they were visiting the beach there, she realized that it might be the place where, 59 years before, her father landed upon. So, she mentions this to her friend, who was also interested in war history of the area, and as a consequence, Zadie is interrogated by this friend. But in the end, Zadie relaizes she knows nothing about his father's war experence. After this event, she returns home and feels determined to start interviewing his father.