User blog comment:Braveangel/About planetary defenses/@comment-217683-20100423043420

The problem here is that you are assuming that the Citadel Council simply doesn't want to (or hasn't thought of) put defensive emplacements in the Citadel. This likely isn't the case. They likely CAN'T put them in the Citadel itself. Remember that 100% of the maintenance and upkeep of the Citadel is performed by the keepers. The Citadel races know very little about how the station runs itself. This is, of course, intentional, as the Reapers have no real desire to allow the organic races on the Citadel to defend themselves.

As for space-based defenses, they have those in the form of the Citadel fleet, and any stationary platforms would be, frankly, foolhardy. Any concerted attack on the Citadel would include dreadnoughts, which could sit back at stand-off ranges and hit the stationary defense platforms with impunity, as the platforms couldn't move or maneuver out of the way like the ships of the Citadel fleet can.

As for Delan's reaction- recall that they are an independent colony in the Terminus Systems, a region of space where ANY interference by an outside government (such as the Alliance) is generally considered an act of war. Is it any wonder he felt the colony would be safer without the Alliance installing weapons systems (and personnel) on the planet? Hardly 'confused thinking'. He simply wanted the colony to remain beneath the notice of the nasty people in the area, which is hard to do when someone forces a nice, big, state-of-the-art weapons system on you.

Lack of what you would deem adequate planetary defenses isn't a 'plot hole' by any stretch of the imagination. It was clearly integral to the plot for the Citadel to be unable to handle the attack of Sovereign and the geth. Ditto for Horizon.The plot wouldn't have worked with the haevy defenses you advocate, and the technology of Mass Effect explains away most of the rest.