User blog comment:Braveangel/About planetary defenses/@comment-2006054-20100423092329

Massing the battle formation, and crossing the mass relay, is not an uncommon practice. The Codex even has a description of it. And thus the coming of an invasion through the mass relay is not something to be unprepared for. And the more defensible a position, I think, the more it will depend on stationary defenses. Mobile defenses, in that case, are only used to screen attackers and hold them at bay while the fortress pound them with bombardment. I think this is a pretty classic military practice.

I don't deny your argument about battleships (having to duck it out) using secondary guns. But then they lose their unique role as battleships. And secondary guns in modern battleships are pretty lame compared to their main guns. And usually very defensive in nature. However, one thing is certain: the main bow gun of the dreadnoughts lose their effectiveness in close combat, and they turn from the hunter to the hunted.

And, yea, I won't go hairsplitting about the Roman/Byzantine dichotomy.