Instead, it is a tragic love story whose farewell is from Frederic to the woman whose arms held sanity in the crazy world of the Great War.
This last sentence of the Enotes page entitled "Introduction" places the narrative into perspective. Disllusioned with war himself, Hemingway writes of an American ambulance driver with the Italian army--a position Hemingway himself held in WWI--who finds himself alienated and questioning traditions and institutions. When he talks with the priest, Gino, or Moretti, Henry separates himself in thought; often his responses are non-committal or distracted, or even rather flippant. For instance, in Chapter XI when the priest visits him after his wounding, the priest tells Henry that when one loves, one wishes to serve; he adds that Henry will be happy when he truly loves.
"I'm happy. I've always been happy."
"It is another thing. You cannot know about it unless you have it."
"Well,"...If I ever get it I will tell you."
Certainly, after he is wounded, Frederic Henry finds himself in a existential state. Having found no meaning in the war, or religion, or any tradition, he searches for personal meaning in a world of absurdities. Hiding under Catherine's beautiful long hair, Henry loses himself to her as she does to him, "There isn't any me. I'm you. Don't make up a separate me." However, after they run away to Switzerland and their baby is born, Frederic Henry loses both. Without Catherine, Frederic, then, must find a separate existence as he steps out into the rain.
Indeed, Frederic Henry's farewell is an adieu to a life with Catherine in which he has found individual meaning, a separate peace in love, a peace from the absurdities of war, the contradictions of religion, and the falsities of institutions and traditions.