Being fought on an interstellar scale, the wars of the Reach must begin in space and work down to the planetary surface. There, one sets up ground bases and tries to maintain or regain the aerospace superiority that let one reach ground in the first place.
Since arable land and usable cities are the main prizes of war in the Reach, there is little use made of mass destruction. Strikes are usually as surgical as possible.
Besides the usual panoply of ships weilding beam-weapons and force fields, Reach warfare includes the following interesting features:
Based on the tectonic missiles used in terraforming, these missiles are miniature versions of the old hyperdrive. They come out of hyperdrive at a carefully calculated distance beneath the target, causing a large explosion when the missile abruptly occupies the same space as the bedrock. The size of the explosion depends on the size of the missile, the depth and structure of the bedrock, and the missile's penetration fraction (because the whole missile never succeeds in re-entering normal state; the hyperdrive itself is always destroyed before that).
Hypermissiles are the nearest approach to holocaust weapons used in the Reach. They have occasionally been used to destroy entire cities, but never larger areas. They leave no radioactive residues.
Defend against hypermissile strikes with tachyon beams, to destroy the missiles or, more commonly, disable the hyperdrive so the missile cannot jump back. Such counterstrikes must be carried out by computer, often involving prescience by cross-time signaling.
The starfaring equivalent of paratroopers are "drop-troopers," and use gravity belts with small, use-once force fields to drop without parachutes from a higher range of altitudes.
Even faster and more spectacular are the hypertroopers. They are injected further behind enemy lines from specially equipped hyperdrive craft, appearing in the upper atmosphere straight out of hyperstate. This deep penetration usually means one of four things:
Besides all the risks faced by a drop-trooper (hostile territory, burning up on entry, crashing, getting lost), hypertroopers risk bad hyperjumps. These most often result is the trooper flying off into hyperstate in a random direction, hoping to be picked up (preferably by one's own side) before life-support runs out. A badly-aimed jump can insert (most of) you somewhere underground, like a hypermissile. A badly-tuned jump can just reduce you to plasma, often along with the rest of the jump ship.
Consequently, hypertroopers are both daring and meticulous, and their support crews are even more meticulous.
These are psionic weapons used to subdue cities. There is no explosion; the bomb induces electrical currents over a wide range, chiefly in flesh. Few people are killed directly by these strikes, but many may be killed in subsequent accidents, thousands injured, and hundreds of thousands may be rendered unconscious or incapacitated for hours. The subsequent demoralization and chaos have great military value without destroying potentially valuable workforces or infrastructures.
Defend against shock bombs with beam-weapons or military psi-conditioners. (The shock bombs, in turn, may be mounted on fast and evasive missiles, or set to new psionic icons. An arms race ensues.)
There are several facets to warfare by communiations link.
Electro-Magnetic Pulse is a simple, effective way to destroy much enemy technology. Ordinary EMP can be shielded against with conductive materials. However, psionic technology can let EMP cross these barriers. Further psionics can shield again, and an arms race ensues.
Fighter pilots are naturally fond of piloting their craft by remote control. Fighter combat then reduces to RC drone fighters trying to battle their way past each other to attack heavily fortified control bases.
Of course, things do not remain that simple. Enemies try to disrupt the psionic telesis link with wide-range psi-conditioners. Other forms of comm link are subject to other forms of jamming. The response is to counter-condition, to keep shifting comm modes, and to endow the drone with enough intelligence to operate during comm black-out.
Once the jamming gets too fierce, though, there is nothing for it but to have real pilots climb back in the cockpits.
Corrupting enemy software is a time-honored part of warfare, in the Reach. In addition to access by espionage, there is access in battle through psionic telesis in various unconventional forms. Such hacking has two phases: first, breaching any psionic protections around enemy systems; second, the purer hackery of inserting code, crashing systems, reading files, etc.
Thanks to psi-tech, ships and other war vehicles can make themselves invisible in a variety of regimes -- electromagnetic fields and radiations, particle emissions, and selected cryptometrics and icon-trails. Also thanks to psi-tech, there are various ways of penetrating these cloaks, and the usual arms race ensures.
In the Reach, patharchy is centuries old and a long-time part of the military skill set for those with aptitude for it:
Psionic medical technology can endow combatants with enhanced resistance to various forms of injury. Permanent resistance scores are expensive, but scores lasting a handful of days can be distributed to troops entering combat. Favored scores are resistance to:
Since they are self-reproducing, self-maintaining, and to a degree self-training, androids are much cheaper than equivalent robot troops. However, they are not cheaper than conscripts, and this limits their use, as does their general lack of initiative. Android troops are usually used by economically centralized governments.
Typical android troops are outfitted exactly as are their human equivalents, though they are not trained together. Android soldiers may also be heavily cyborganized without consideration for convenience or reversibility.
Even when not cyborganized, android troops are usually clearly marked to distinguish them from human. The all-black marker eyes are traditional. Individual services often color the entire android in military colors (e.g. olive green infantry androids, navy blue naval androids, black and silver spacer androids). Tattoos of rank insignia and ID numbers are almost universal.
Viruses and microbes can be gene-tooled to attack wide or narrow target populations with a large range of debilitating effects. A single general could be selected, or a few bloodlines that compose a large section of a particular city's or planet's population.
Defend against smart germs with more transgenic microbes ("smart phages"), antisepsis, decontamination with psionic and hv catalysis, and adaptive antibody complexes ("smart antibodies").