Ultra Box (referred to as Four Horsemen in later editions of the games) were a squad of 4 elite assassins that specialized in close-quarters-combat and were sent to assassinate Solid Snake, the titular protagonist of Metal Gear 2: Solid Snake.
The Four Horsemen were composed of units originally aligned to the SAS, GSG-9, and UDT. They took orders directly from Zanzibar Land's president, Big Boss and his second-in-command, Gray Fox, and were only sent in to deal with threats that Big Boss and Gray Fox took very seriously (or in other words go after "the big fish").
Metal Gear 2: Solid Snake
In Zanzibar Land's tower, the Four Horsemen found and fought Solid Snake in the central elevator. Despite their skills and numbers, however, Snake beat and killed all of them single-handedly.
- They were named after the terrifying Biblical figures from the Book of Revelation known as the "Four Horsemen of the Apocalypse". Their original name, likewise, was named after the British band Ultravox.
- Ironically, the Ultravox song "Dancing With Tears In My Eyes" appears in Metal Gear Solid V: The Phantom Pain.