The night was dark as they groped forward as slowly and silently as possible. Every sound brought them all to a stand still, each ear straining to identify the noise and the cause. When a small rock slide came tumbling down off to their left they almost opened fire. Their armors external pic ups bringing every sound in to them. They were a squad of U.N. Spaceborne Infantry. They had been on Mars for the last three months, the S.I. had been formed twelve years earlier as a direct result of threats to humans on other planets. The only problem was that most of these threats were from other humans. Various racial hatreds, religous biases, organized crime, pirates, lunatics, etc. The U.N. Police Force was responsible for law enforcement on many of the colonies, they were armed with older military equipment that was still useful. They had put up a good fight, here on Mars. Bullet riddled U.N.P.F. facilities, usually with everyone dead inside, were all over. Then again, so were several civilian facilities. That was the difference between the U.N. and the Machines, the U.N. had rules against mass slaughter of innocents. The Machines were intent on wiping humans out, which they had found to be inferior beings and a threat to the Machine Collective. The individual Machine infantry and space/air craft were controlled by one general computer. This Machine was actually an Artificial Intelligence that controlled the individual units via a faster than light link networking them all. They were much more heavily armored, bordering on almost indestructable, than the regular units. The infantry models came in three main configurations: 1.) The bipedal version which could change color like a chameleon to suit the landscape, they stood about seven foot tall and weighed a solid ton, usually armed with the same kind of assault rifle the U.N. forces used. They were humanoid shape, their faces being semi human, they had mouths which were just covered speakers, they had eyes that glowed green which had the ability to see in any spectrum. 2) The tracked version which mounted twin miniguns, stood about twelve foot tall, and ended in the same head as the bipedals. 3) The tracked version with miniguns and mounting rocket launchers in its body