An important symbol of machismo (an exaggerated sense of manliness and domination) is the helmet that the Lieutenant offers Thomas Fowler when he travels to Phat Diem, a dangerous war zone. Fowler confirms his machismo—and his indifference to his own life—by turning down this important protection. Later, Alden Pyle accepts the helmet, seemingly without any second thoughts. The symbolism is clear enough: Pyle is young, innocent, and optimistic—thus, he wants to live. Fowler is older, more experienced, and comes bearing more suffering. As a result, he’s less interested in life itself, and therefore has little drive to continue to survive.