Aside from the cutscene known as "Hallfight" from its filename, there is almost no mention of ground-based combat in the FreeSpace universe. Hallfight forces a few commonsense conclusions on the nature of GTA weaponry, namely that it really can't be traditional guns based on its caliber and the sort of noise it makes. Beyond that, extremely little is known about weapons and tactics of FreeSpace-era ground combat, though it is frequently pointed out that most FreeSpace fighter missile weapons are equivalent to modern tactical nuclear weapons and so probably unsuited to atmospheric use.
There are only two canon references to ground warfare in the FreeSpace universe. If the player successfully completes the first mission in FreeSpace 2, s/he is told that 600,000 ground troops are sent to invade Cygnus Prime. Also, there is a Descent:FreeSpace multiplayer mission where the player attacks an HoL marine convoy.