Contrary to what their name seems to imply, the "'Robotech Defenders'" are not part of the Robotech anime universe adapted by Carl Macek and released by Harmony Gold USA, but they did adopt the same moniker and logo.
It shares many common themes with other science fiction series of that time, including invading aliens, and giant mechanical war machines.
One of the features of the models (excepting the Human and Grelon miniatures) was that they were not static, but had fully movable joints and removable equipment.
In the North American market, the models met with some success, appealing to both fans of Robotech and the players of Battletech tabletop strategy game.
In the end, both companies decided to enter into a co-licensing agreement and the name Robotech was eventually adopted for the syndicated television show that the home video line had transformed into.
The reason for this is that all of the original edition's 'Mech visuals were based on designs from a variety of anime series, including Macross, Dougram and Crusher Joe, some of which Revell kits are sourced.
The story followed the battles of a team of pilots who fight a savage race of aliens, called "Grelons", who have invaded all planets of a star system using superior technology.
Each of these units has a unique range of abilities and environmental specialties (e.g., Aqualo was capable of diving and sea-based activities, Ziyon's Element was cold and snow, Thoren's heat and magma, Gartan's urban combat).
They escape by pushing a big red button which releases the Defenders' minds, unleashing the latter's' full combat capabilities.