23rd Century Powered Infantry

The 21st and 22nd century soldiers who fought the Unification Wars were equipped with what was then extremely advanced body armor and weaponry, but the fighting suits utilized in the Third Frontier War are an order of magnitude more sophisticated and capable than anything seen before on the battlefield.

The modern suit of armor was made possible by advancements in nanotechnology, which facilitated the miniaturization of various operational systems.  The development of a nuclear power source small enough to be carried as part of a trooper's kit caused a quantum leap in the amount of firepower and destructive force possessed by the armored infantryman.

The massive increase in energy available to power the suit led to an increase in defensive strength, as weight concerns became far less important.  The availability from colony worlds of materials that were extremely rare on Earth facilitated the creation of more sophisticated designs for armor plating, increasing the survivability of the soldier and creating near-invulnerability to any enemy not themselves armed with the most powerful weapons.

The Model 7 armor worn by Western Alliance troops is constructed of a multi-layered arrangement of steel, osmium, iridium, and a variety of polymers.  The result is an extremely hard and dense, yet not at all brittle, metal suit, which provides excellent protection against virtually all types of small arms.

The suit has highly developed servo-mechanical systems that allow the marine to walk, run, and take other actions almost normally, with the suit interpreting the move from the wearer's motions and executing the desired action.  The armor provides greatly amplified speed and strength to the user, and significant training is required to develop proficiency in controlling and utilizing these capabilities.

The atomic power source of the suit also allows the trooper to carry weapons that require an enormous amount of energy.  The Model 7 suits currently in use have a modular design that can accommodate four mission-programmable weapons systems.
The primary infantry weapon for fighting in an Earth-like atmosphere is the Gaussian Magnetic Rifle (GMR) version 3.2.  The mag-rifle is a multi-stage coilgun firing a small iridium or depleted uranium projectile at a velocity of over 60,000 meters per second.  It is capable of breaching powered armor and virtually shredding normal steel and plasti-steel constructions.  Because the velocity delivers so much impact energy to the target, the projectile itself can be very small, allowing a magazine to hold 500 rounds and enabling automatic fire without immediately depleting ammunition reserves.

Troopers have a variety of support weapons, such as a mag-powered grenade launcher that is capable of firing a wide variety of rounds, including explosive, incendiary, fragmentation, chemical, and even nuclear, though atomic weapons are rarely deployed at the level of the individual soldier.

There are a number of energy weapons as well, which are used primarily in low-density atmospheres and vacuum conditions.  The most commonly deployed are portable particle accelerator units, lasers, and the laser-blaster, a very high-powered short-range pulse laser.

The Model 7 suit is capable of sustaining its wearer in virtually any environment, including deep space.  Various systems are included to accommodate bodily functions and deliver intravenous nutrition and hydration.  The suit also has a sophisticated medical monitoring and trauma control system designed to medicate a wounded marine and administer whatever first aid is possible pending pickup and transfer to a med facility.
The trooper is assisted in operating the suit by an artificial intelligence computer system that communicates verbally with the marine, eliminating the need to physically touch controls to achieve desired results.  The AI also monitors the trooper's physical condition, and administers medical or nutritional supplements as required.

The Model 7c command fighting suits used by officers are outfitted with a much more sophisticated AI.  Trooper AIs are mostly concerned with assisting with the needs of the individual soldier.  Officers have a far greater stream of information into and out of their communications systems, and the officer AIs are designed to help control this data flow.  The officer AIs are quasi-sentient computers, with developable personalities.  An officer's AI is able to grow and alter its personality in response to stimuli and communications from the user.  This often leads to unpredictable results, including common complaints that the AIs are churlish and difficult.  Generally, this sort of user-AI interaction serves to reduce the overall battlefield stress experienced by command personnel, though many of these officers would disagree, some of them in quite colorful terms.

Beyond the heretofore unparalleled suite of equipment, the powered infantry trooper is the most trained and educated soldier in human history.  Western Alliance training is a six year program including physical, classroom, technical, and operational segments.
A planetary assault is a very tightly planned and executed affair.  Troopers are typically put on pre-assault intravenous feeding programs and injected with a cocktail of narcotics designed to increase reaction speeds and stamina.

When the powered infantry solider hits the ground on a target world, he or she has all the equipment and preparedness that technology, medicine, and training can provide.