Corporal Timothy Yorba was a Sentinel who participated in Operation Iron Fist. His team was led by Lt. Nathan Hale, and their mission was to infiltrate a Chimeran facility and acquire a nuclear fuel cell. The team infiltrated the base through three captured Stalkers and later using the machines in destroying the Chimera's defenses once their cover was blown. Yorba had placed demolition charges on the Stalkers as the Sentinels prepared to enter the base, just in case they desperately needed to destroy the vehicles in order to create a diversion. He also utilized his expertise to open the doors leading into the base. Yorba was wounded during a firefight on the roof of the facility, but was able to continue fighting due to his regenerative abilities, and survived to complete the mission.