System Defences; a superficial analysis

Some of you will, I know, be wondering why initial investments in system defences are so cheap.

It's because they're of very limited utility. On a six, they always fail, no matter how much you've put into them. That's why there's an arbitrary lower limit on the size of force which can be used to enter a system with hostile intent - absent that, a succession of weasel boats would fall on the homeworld turn after turn and on average by the end of turn six, your capital would be in ruins, even if you had system defences which required an entire starting fleet to take on at even odds.

What bigger defences do is make it more likely that an unsuccessful attack will hurt - by raising the size of a fleet needed to attack with impunity and by raising the damage which a defeat will inflict on the unsuccessful attacker. So people will either stop and think about the risk of defeat or they will go in having massed something serious. It's worth keeping in mind that attacking with less than the system's strength gives you a one third chance of a bloody nose versus a one-sixth chance of victory.

The damage inflicted by system defences isn't that heavy either (though poor management can make it a lot worse - there's a lot to be said for planning to move into the system which an enemy fleet might retreat into if defeated - you'll force them into combat before they can do repairs and neglected system defence damage is intentionally simple and nasty). So they shouldn't cost anything like as much as starships, which are capable of moving around, forcing a decision, and above all don't give up the ghost completely on a single dice roll.