Where there are people, particularly in large groups separated by distance (and by proxy culture), there will be war. The harshness of the environment or emotional and physical costs to the soldiers, history has proven, is irrelevant.
Combat ships will be largely unmanned, with several (for redundancy) manned "overseers" nearby to give the drones a sentient strategic advantage. Remote oversight wouldn't be able to respond quickly enough due to communications lag, although the overseers would be in two-way communication with more distant officers coordinating the combat groups general strategy.
Assuming the technology to efficiently and compactly generate incredible amounts of power has progressed equally with all other fields relevant to space colonization, energy weapons would be favored over more conventional chemically-propelled/detonated ordinance like bullets, missiles and bombs. Conventional ordinance requires mechanical fidelity and precision to fire, is limited in quantity to due to the mass required to be effective, travels slowly over great distances, may be easily impeded by other ordinance or energy weapons, suffers from intertia and can result in friendly fire if it is disabled, misses its target, or is fragmented by defensive countermeasure. Energy weapons reach their target nearly instantaneously, may track their target for sustained, precision delivery, and use only enough energy to obtain the desired effect. Their vector can be controlled non-mechanically, allowing sensors to maintain a lock on a rapidly and unpredictably moving target. They may not be impeded by other energy weapons and travel too quickly to be countered by dynamically-deployed mass-based countermeasures.
The precision and accuracy of combat drones' movement and energy weaponry combined with the tiered progression from automated drone to human overseer would, with the exception of any extreme tactical choices by central command, product a general lack of chaos that is atypical of conventional battles. The primary focus would be to edge out the opponent by obtaining slight defensive advantages through technological superiority, use of unique environmental factors (planets, moons, stars, gravitational or radiological fields, asteroids), the purposeful introduction of unpredictable or chaotic elements (literally gambling that the increase in chaos will be favorable), or psychological tactics such as deliberate attacks on civilians, propaganda and public (broadcast) executions and torture.
The bottom line is that less people would die. Once the enemy drones have been decimated there's really no reason to go on slaughtering the general public. Once that happens the first few times, history will keep the losers of the future in line outside of the inevitable (but manageable through surveillance and information control) insurgencies.