Master Sergeant John Magnusson was Frank Keegan's squad leader in Medal of Honor: Vanguard. He was a great leader and a solid tactician saving many lives of his fellow paratroopers. He fought through the Italian campaign with the squad, proving to be an exceptional leader. His squad looked up to him with high respect. During Requiem, he was killed by a German sniper while helping Keegan up. Keegan then takes up the role of squad leader and a promotion.
Sergeant Magnusson led Keegan's squad throughout Operation Husky. The C-47 he was in was shot down, however he survived, he then ordered his squad to fight their way through a boat house and streets guarded by Italians with his squad. After reaching the centre of the town his squad came under attack by Germans, however Magnusson and his squad fought their way through them until they reached the coastal bunker and destroyed the coastal guns. After destroying the guns he gave a speech and moved 20 miles west to regroup with the rest of the 82nd Division.
During Operation Neptune, Sergeant Magnusson's parachute got caught on the broken roof of a church, causing him to be captured by the Nazis. Keegan and Garrett fought their way up to him and rescued him from the church, however Keegan was incapacitated by a buttstroke from a Karabiner 98K by a Fallschirmjager. After Keegan recovered from being struck in the head, he gave to order to his squad: 'Let's get moving before the Krauts get more dug in!' and him and his squad fought their way through the cemetery near the church until they reached the first bridge, which was then destroyed by an explosive charge. Sergeant Magnusson then split from Keegans group to find more bridges to destroy. After an explosive charge on a bridge prematurely detonated, incapacitating Keegan, Sergeant Magnusson went to help Keegan but was killed by a German sniper in the process.