The man at her dinner table was a stranger. He hunched over his food and wrapped his arms around his plate, spooning marrow bone broth into his mouth as if the meal were a timed event. When he realized what he was doing, he flushed guiltily [...] He jumped at every sound and flinched when he was touched, and the pain in his eyes was impossible to miss. 

This quote can be found in Chapter 35. Vianne is just old enough to remember World War I. She saw her father, a formerly loving man, transform as a result of his traumatic experiences in the trenches. When Antoine returns from imprisonment in Germany, she knows that he is not the same man he was when he left. Still, she is surprised by his transformation, which is both physical and psychological. His experiences have clearly scarred him, and though he is safe at Le Jardin, he continues to eat his meals quickly, as if he is in danger. She observes that he has become anxious and jumpy, as if he is still mentally at war.    

I remember the men who came home on crutches, their pant legs empty and flapping, or an arm gone, or a face ruined. I remember how Papa was before the war—and how different he was when he came home, how he drank and slammed doors and screamed at us, and then when he stopped. I remember the stories about Verdun and Somme and a million Frenchmen dying in trenches [...].

In Chapter 8, when Maréchal Pétain announces the surrender of France to Nazi Germany, Vianne and Isabelle have very different reactions. Isabelle is shocked that France would capitulate so quickly to the enemy, where Vianne is relieved by what she thinks will be a quick end to the war. Vianne accuses Isabelle of naivete, arguing that her younger sister does not remember the First World War and does not understand how profoundly the soldiers were traumatized by their experiences. Here, she reflects upon her father, who became angry and unkind after fighting in the trenches. Her response registers the transformative effects of trauma, which affected her father and an entire generation of men.  

For the first time, she saw her own childhood as an adult, from far away, with the wisdom this war had given her. Battle had broken her father; she had always known that [...] It had broken him. “You girls will be part of the generation that goes on, that remembers,” he said. “The memories of what happened will be…hard to forget.”  

In Chapter 33, when Julien announces his plan to sacrifice himself for Isabelle, Vianne reflects upon his traumatic experiences in the First World War. The war, she notes, “had broken her father.” Previously a loving man, he was unable to return to ordinary life after the war was over, retreating from his family and ultimately abandoning his daughters. Now, Julien pushes Vianne to think about how the war will affect her own generation. Her generation, he argues, will face the difficult task of persevering despite the trauma and the painful memories which will be “hard to forget.” The war, he suggests, will affect the population of France in profound and complicated ways.