From Halopedia, the Halo wiki
Walpole was a UNSC Marine sharpshooter and Orbital Drop Shock Trooper stationed at Earth in 2552. He was under the command of Gunnery Sergeant Marcus Stacker, part of the 7th Orbital Drop Shock Trooper Battalion of the 105th Shock Troops Division.
During the first day of the Battle for Earth, Walepole and his squad were dispatched from the UNSC In Amber Clad from Cairo Station to relieve the UNSC's ground forces and to board the Covenant assault carrier, Solemn Penance. Shortly after deployment, their D77-TC Pelican dropship was shot down over Old Mombasa by a Type-47A Scarab walker. He survived the crash, but his squad was soon attacked by a Covenant patrol.
When the squad was pinned down by a Kig-Yar Sniper, Walpole as the squad's sniper, neutralized the Jackal with his "welcome-to-Earth gift basket", causing the lance's Unggoy to flee the area. A camouflaged Sangheili then snuck up on the squad and took Walpole hostage by holding an energy sword held at the sniper's throat. One of Walpole' squadmates, Butkus, wielding an overcharged plasma pistol, along with Stacker using his BR55 battle rifle, killed the alien and freed Walpole. Walpole's subsequent fate is unknown, as his Sergeant, Stacker, was later found in the city without his squad present.
Personality and traits
Like all ODSTs, Walpole is very tough and professional. He is an excellent marksman, and is not afraid of enemy snipers. He also has a notable sense of humor, even in combat, as evidenced by his desire to provide the Kig-Yar a "Welcome to Earth" 'gift basket'. When he is being held hostage by a Sangheili, he orders the team to kill the Sangheili instead of saving him.
List of appearances