- "You're not crazy enough to shoot me!"
- — Guzzo, when McCullin threatens to shoot him.
- "As far as Guzzo is concerned, his role in France is to live and that's all - no matter what it takes or who he steps over along the way."
- — Call of Duty 3 bonus materials section.
Salvadore Guzzo's hometown is Boston, Massachusetts. During the war he became a radio operator in the 29th Infantry Division. He was later transferred to the 90th Infantry Division due to a shortage of men. Guzzo first joins Nichols's squad in Saint-Lo after Nichols learns his CO was killed in Martinville. When Guzzo is first ordered to be transferred into McCullin's unit, he is reluctant to join. At Saint-Lô, Guzzo and Nichols receive minor injuries when a tank explodes and sends them tumbling into a wrecked building. Later, as the battle progresses, tensions grow between Guzzo and McCullin and the two end up having a major falling out near the end of the battle. Sgt. McCullin holds a gun at Guzzo and threatens to shoot him for desertion after Guzzo suggests they should fall back. Guzzo views McCullin as insane, and McCullin sees him as a coward. During the battle for the Mayenne Bridge, Guzzo says McCullin has gone crazy and shortly before the Sergeant dies, McCullin's last words are "Tell Guzzo to go to hell."
At the final cutscene in the level "Forest", Dixon is tired of Guzzo's attitude to him, telling him that "The Sarge may have put up with it, but I won't."
During "Chambois", Guzzo saves his comrades' lives by risking his own to call in air support to level the German forces. While marking targets with flares, Guzzo gets shot in the leg. After carrying Guzzo to safety, Dixon too gets shot, and is fatally wounded leaving Guzzo in charge of the squad. After Dixon's death, the enraged Guzzo leads the remaining American forces to victory.
After the battle, Guzzo officially becomes the leader of the squad. At the end of the game, he is seen quoting Sgt. McCullin's "One rule" while talking to the new recruits in the supply truck.
Guzzo is often irate and unhappy with his orders. He doesn't get along with his fellow squad. He and McCullin share a mutual dislike of each other, which causes discomfort within the squad until McCullin's death. Guzzo becomes the squad leader after Dixon is killed, and essentially changes his attitude. At the end of the game, he becomes a responsible and strong-willed leader, he also quotes one of McCullin's rules and wears his helmet, implying that he no longer thinks of McCullin with scorn.
- In the second level, Guzzo has been demoted to Private for attempting to desert, but is later a PFC again.
- In the end, Guzzo repeats McCullin's rule, "You're no good to me dead!" and the private next to the player replies with, "What kind of pep talk was that?" to which Huxley takes Dixon's role, saying "You want inspiration private? Read a poem."
- Guzzo is seen wearing McCullin's helmet in the ending cutscene.
- Guzzo is always seen with a radio on his back until the final cutscene where he has a regular backpack.