Space Combat
Space combat works by landing a fleet of soldiers onto another planet. Often, a soldier wears a combat spacesuit, like the normal suits we have today, but coated with a thin layer of steel on the inside to protect it against any external breaches. This makes the suit slightly more bulky to move around in, but prevents a lot of deaths from decompression
If a bullet manages to penetrate the suit, in a low-pressure environment, this usually means a painful death. This is why combat is so feared by a lot of militaries, as one single shot going through your suit usually means your demise.
Weapons were never changed significantly in the past 2 centuries. This is due to a lot of things, such as innovation not really being required (a single shot can still kill), and the fact that spending more resources on a design that's already good is unnecessary. Very often you still find early 21st century assault rifles and pistols still being given to soldiers.