Andrea Stavros was a large Greek man and longtime friend and ally of Captain Keith Mallory. A former lieutenant colonel in the Greek Army, he'd served as Mallory's trusted lieutenant during a mission in Crete. He had a tragic past. Mallory considered him such a close friend and confederate that he often thought of Andrea as his "alter ego" and "doppelganger" in many ways, due to his resemblance to Mallory. Despite his great strength, he was a very patient and even-tempered man.
Mallory asked him to come along as part of Lieutenant Andy Stevens' team because Andrea spoke excellent Greek and knew the culture of the Navarone islanders well. Once on Navarone, he proved invaluable to the group, and killed the cruel German officer Captain Skoda. After the destruction of the guns of Navarone, Andrea, Mallory and the other surviving members of their team were rescued by the crew of the Sirdar.
A former colonel in the Greek military, Andrea Stavros conducted numerous black ops missions during World War II. He was wanted by the Germans for his actions against them. At one time while he and Keith Mallory were working together, he was away from home and Mallory agreed to let some wounded Germans stay near Andrea's house. The uninjured Germans, eager to kill Andrea, who they didn't know was away, killed their own wounded and bombed Andrea's house, killing his wife and children. Later, Mallory helped him bury them. Afterward, Andrea said he blamed Mallory for his family's death, and vowed he'd kill him when the war ended.
Nevertheless, the two continued working together on numerous undercover missions even after that. When Mallory was chosen by Commodore Jensen to assist Major Roy Franklin on his mission to Navarone, Mallory specifically requested Andrea. Despite his vow to kill Mallory, Andrea saved his life while the two were climbing the cliff on the island. When Mallory slipped, Andrea grabbed his hand. Andrea's skills as a covert assassin proved invaluable. At the top, he dispatched the lone soldier patrolling the cliffs. Later, when the group were being hunted by German troops on Mount Kostos en route to St. Alexis, Andrea used a sniper rifle to pick the approaching Germans off one by one to buy his comrades time.
When the group met up with Spyros Pappadimos' sister and resistance leader Maria Pappadimos at St. Alexis, Andrea became smitten with her, and the pair developed a close friendship over the course of the mission. The mission to destroy the guns was sidetracked when they had to take the injured Franklin to a doctor in Mandrakos, where they were captured by Lieutenant Muesel and interrogated by him and Captain Sessler. Andrea lied about his identity, claiming to be a poor fisherman from Cyprus named Nondus Salonikus; Muesel had his military file complete with a file, however, and so that ruse failed. Next, when Sessler attempted to torture Franklin, Andrea feigned being violently ill.
Sessler ordered him taken out. When he was seized, Andrea attacked the guards and grabbed Sessler in a chokehold, allowing Mallory and the others to get their guns and capture the Germans. When they took the Germans' uniforms, Andrea donned one belonging to one of the guards. To pass as a German private, he had to shave his mustache (a look Maria liked).
When the time came to destroy the guns, Andrea's role in Mallory's plan was to join Spyros in luring the bulk of the German forces away from the gun fortress by causing general mayhem in the neighboring town so that Mallory and explosives expert Corporal Miller could get inside. He used guerrilla tactics, whilst the more impulsive Spyros openly confronted a German officer and was killed. After both he and Mallory had fulfilled their objectives, Andrea dove into the sea and swam out to a boat Maria had stolen and already picked up Mallory and Miller in.
Andrea, weary, almost didn't make it. Mallory seized a boat hook and held it out to him. Andrea, thinking Mallory meant to kill him, flinched away, until told to grab it. Finally he did, and Mallory pulled him safely aboard.