GEV was the second game in the Ogre microgame series. Short for "ground effect vehicle", those units were essentially armed and armored hovercraft, at a time when hovercraft were imagined to be the transportation of the future.
Don't hear much about hovercrafts these days. Main battle tanks still command top spot for ground-based military units, but in the 1980's it was neat to imagine wars of the future being fought by hovercraft and other unconventional units.
GEV takes up the baton from Ogre, venturing into territory every Ogre player wanted to explore: battles between the regular combine and paneuropean combat units. Ogre gave us the supertanks. GEV introduced some new units that Ogre players were clamouring for.
Units like the light tank. That unit was half as powerful as the heavy tank, but that meant you could purchase twice as many. The profile of the light tank was interesting, as it looked similar to the Ogre, what with its forward communications and sensor suite tower.
The mobile howitzer was a welcome addition, as the fixed howitzer always felt too vulnerable. As the defender, I was loathe to use the fixed howitzer in my regular Ogre games, despite the effectiveness of the four howitzer strategy.
GEV also gave us an additional infantry unit option -- the one strength unit infantry counter -- and gave all infantry units additional firepower in overrun situations. Prior to that, infantry was incredibly fragile. Infantry was one of the few units that used the old box-and-cross symbol, rather than giving us unit silhouettes.
As I recall, we had to wait for the Battlesuit microgame before infantry silhouettes were finally provided.