A pacifist finds his values challenged by the outbreak of World War II.

On the home front during World War II, advertising art director Susan Cahill, put off by her boss and fiancé Paul Clemson's flirtation with a potential client's daughter to assure that he secures a contract, accepts agency artist Alexander "Alec" Austen's dinner invitation one night. Afterward at Alec's home, Susan is disturbed to discover an emotionally revealing portrait of herself drawn by Alec and abruptly ends the romantic evening, but agrees to a date the next day. After she leaves, Alec finds a telegram to report for active naval duty and decides not to tell Susan as they continue to date. Several weeks later, Alec takes Susan to meet his mother, a Quaker, and announces that he and Susan are to marry and that he will soon be leaving for active duty. His mother is shocked to learn that Alec has secretly been serving as a lieutenant in the reserves and laments that he has chosen a path so contrary to Quaker pacifist principles. Susan admits that although she loves Alec, she is betrothed to Paul and will not break the engagement because she is indebted to the executive for her career. Boarding the U.S.S. Poe at the Brooklyn Navy Yard days later, Alec meets the other officers aboard: commander of the ship, Cmdr. Warren Meredith; Alec's bunk mate and the ship's doctor, Lt. Blanchard and Alec's immediate commanding officer, Lt. Comdr. Mike Edge, a short-tempered war veteran who berates him for being a Quaker. As the ship makes its way to the Aleutians, Alec befriends the men in his regiment, gunnery mates who entertain themselves with gambling and thoughts of women. During an operation to collect survivors from a sunken German submarine, Edge vengefully refuses the prisoners food and then confronts Alec about his politics, but Alec assures him that he can "hate" like the rest of the men. Later, when Blanchard finds the drawing of Susan, Alec sadly admits his heartbreak over her refusal to marry him. Days later, while the ship is being refitted at a San Francisco shipyard, Alec's regiment goes to an Armenian bar, where Pvt. Aaron Slobodjian introduces his comrades as his cousins to the lonely Armenian women customers, who dance and dine with the men. Meanwhile, Alec remains at the dock drawing a portrait of his friend and regiment lieutenant, "Frenchy" Shapiro, who explains that the portrait is for his estranged daughter to remember him by. Soon after, Susan finds Alec on the docks, having prearranged the meeting with Blanchard's help, and announces that she has broken her engagement to Paul, found a new job and eagerly wishes to marry Alec. With plans to marry during his leave, the couple meets Susan's sister Claire Innes and her two boys in Pebble Beach, California. While visiting, Claire receives word that her husband has been killed in action. Watching the sisters weep, Alec decides that he cannot risk Susan becoming a widow as well and promises to marry her only upon his return from duty. Days later at sea, when an aircraft is spotted on the radar, sailors await Alec's orders to fire, but he freezes. As the American fighter comes into view, all are relieved by Alec's "decision," but that night Alec admits to Meredith that only fear, not knowledge of the plane's identity, prevented him from giving the command. After Meredith transfers Alec to damage control and Edge condemns him, all but Frenchy lose faith in Alec. Weeks later during an enemy attack, a bomb crashes through the deck without exploding. With Frenchy's help, Alec dislodges the bomb then throws the live explosive overboard, where it explodes. During a funeral service for Aaron and another man, who were killed in the attack, Edge, who has hidden his addiction to morphine, panics at the memory of others lost in battle and raids the ship's medicine cabinet for the drug. Meanwhile, Meredith, aware of the animosity towards Alec, reminds the men that they all might have died without Alec and Frenchy's bravery. While docked at Dutch Harbor, Alec punches a marine in a squabble over a jukebox, prompting a brawl. Victorious, the navy men carry the jukebox and an unconscious Alec back to the ship. When he comes to, Alec admits to Blanchard that he felt the need to kill, but Blanchard reassures him that his aggression was natural. Later, as the men solemnly listen to one of Aaron's Armenian folk records on the jukebox, a disapproving Meredith signals his acceptance of the confiscated jukebox by insisting that the men paint it gray, the color of all Navy, not Marine, property. Later, Alec and his men volunteer for a dangerous assignment retrieving stranded soldiers and critical photos of enemy territory from a Japanese-held island. Soon after, Blanchard catches Edge stealing morphine and isolates him in doctor's quarters, where he deliriously rants about Alec putting his men in danger by volunteering to take command of the mission. However, Alec and his men have already reached shore in two rubber boats and make their way up the rocky coast, where they spot the stranded soldiers. Boxed in by Japanese soldiers at the shoreline, Alec orders his men to open fire and signals the ship to bomb the coastline. Dozens of enemy soldiers are killed, but Alec cannot bring himself to fire one shot. As Frenchy and Alec cover the men making their way back to the boats, a wounded Japanese soldier limps toward them with his gun drawn, but Alec still cannot shoot. After killing the soldier, Frenchy openly pities his friend for not being able to fire. When watching four enemy soldiers suddenly attack and wound Frenchy, Alec kills them to protect his friend, but Frenchy dies before they make it back to the ship. Soon after, an injured Alec is discharged and returns to Susan's welcome arms with plans to marry her and deliver Frenchy's portrait to his daughter.