This article examines sexuality in Ernest Hemingway’s novel The Sun Also Rises alongside warfareevents and memories brought home from the frontline. This essay argues that witnessing the war firsthandand the unique circumstances from serving on the frontline has the potential to inspire homosexual tendenciesamong soldiers. This proposition can explain the veterans’ performances in the novel, such as Jake Barnes,Bill Gorton, Count Mippipopolous, and Harris Wilson. In varied places in this paper, the discussion dependson Menninger’s (1948), Fussell’s (2000, 2009, 2013), and Crouthamel’s (2008, 2014) accounts of the influenceof modern wars on soldiers’ sexualities. As this current study shows, in an attempt to hide their newly-foundhomosexual tendencies, the veterans in The Sun Also Rises tend to over-assert their heterosexuality and avoidall nonveteran male environment (s). Reading the novel with Hemingway’s male characters’ performance ofheterosexuality and avoidance leads to new ways of understanding the novel as the current paper discussessexuality in the context of frontline memories and experiences.