Fortress led by Lyle Stenning and his right-hand man Santiago is a paramilitary criminal organization based in the U.S., which is just shy of being a terrorist group. Their manifesto is "America for Americans", and they have set out to "defend" their country by any means necessary to achieve this goal. But in reality, their actions reveal that their self-proclaimed "patriotism" is merely a ruse to justify their criminal activities.
Stenning was put behind bars by Steve Austin, and since then Stenning and Fortress have nursed a grudge against Austin, Oscar Goldman, and the OSI as a whole. Austin would later be called out of retirement to do battle against Fortress, with the help of his son, Michael Austin, and Jaime Sommers (Return of the Six Million Dollar Man and the Bionic Woman).
- Unlike James Bond's SPECTRE, the bionic franchise never went in for featuring a recurring criminal organization as a nemesis. Fortress and "The Company" from The Solid Gold Kidnapping are pretty much the only examples, and they only appeared once each.