What the most amount of missiles can a country have?

How much SDI should a country have?

1 missile per 250 acres.

how much sdi totally depends what are you doing, if you grab land and break gdi then it'd be good to have max sdi but still even with maxed sdi some missiles get thru and even 1% sdi can stop missiles.

So how do you break gdi again?

attack against same country 2 times or do 1 special attack (like missile attack) or 1 harmful spyop.