In terms of characters and characterization (versus plot and theme), A Farewell to Arms is the story of Lieutenant Frederic Henry and the way he grows and changes, lives and learns, in order to catch up to the Nurse Catherine Barkley with respect to experience and the wisdom that it brings. Especially considering that Ernest Hemingway has been accused of misogyny, it is fascinating to note that Catherine is the more mature of the two characters when they meet; therefore, it is Henry who must struggle to match her level of maturity.
Returning from his leave near the start of the novel, Henry knows he should have traveled to the priest's home region of Abruzzi, a "place where the roads were frozen and hard as iron, where it was clear and cold and dry and the snow was dry and powdery and hare-tracks in the snow and the peasants took off their hats and called you Lord and there was good hunting." Instead he has visited bars and whorehouses in the cities of the lowlands. For now, Henry's strategy vis-à-vis the war specifically and the unpleasantness of the world in general, could be referred to as obliteration, which he achieves via alcohol and sex. He is spiritually lost when we meet him, and A Farewell to Arms will trace his movement toward an understanding of the world and of himself.
It becomes apparent as soon as they meet that Catherine is different — more mature, in a word — and the characters' contrasting levels of maturity are demonstrated by their different attitudes toward the war. Henry suggests "Let's drop the war." With her characteristic mix of wisdom and humor, Catherine replies, "It's very hard. There's no place to drop it." Permanently scarred by the loss of her fiancé, she already knows that the war can't simply be "dropped."
