Nether Earth is one of the earliest computer strategy games taking place in real time. It was released for the Amstrad CPC, ZX Spectrum and Commodore 64 in 1987. It was published in the United Kingdom by Argus Press Software and re-released in Spain by Mind Games Espana S.A.
The player takes the control of the human side in a war against the mysterious Insignian race. All of the warfare is carried out by enormous military robots.
The player controls a flying machine which can fly over any part of the play-area. The player must build robots and give them orders to attack Insignian robots and capture neutral or enemy factories to increase production and thus aid the war effort. The ultimate objective is to capture all the enemy bases and thus win the war. Everything takes place in real-time with the action being ongoing rather than turn-based. Because the player's view of the battlefield is limited to where their flying-machine is, much of the front-line fighting is left to the machines whilst the player concentrates on building more robots. The game is displayed in forced-perspective isometric graphics.
A freeware remake of Nether Earth was completed in 2004 and is available for download on the internet.
Another game using almost the same system, for the planetary combat, is Space Rangers 2: Dominators.
Source: Wikipedia, "Nether Earth," available under the CC-BY-SA License.