This is a false assumption Trying to cordon of the area through building a layered system requires quite a bit of depth. geographical depth, even the best long range "protection" is going to have a very hard time making intercepts. Fighters do not approach sites in a linear manner nor is it a set piece battle with individual systems "dueling" each other. Stand off munitions exist that can tag radiation sources from 250Km out and are becoming very common. Not to mention that even mobile SAM platforms will have a hard time getting around under surveillance..there is a reason that air defense sites alone do not comprise the solution for sanitizing one's air-space. Not to mention, there WILL ALWAYS be gaps, and there are various platforms which can exploit these gaps quite well. Eating a Hammer or a Spice will not do the gap-filler radars or MRTRs any good. In such scenarios it is the heavies which exploit their range to avoid all ADGE threats and interceptors - allowing them to ingress and strike from alternative routes which adds up to the ability to create localized air superiority sectors.
The components of an integrated air defense system like the IACCS are many in number and quite expensive- just the underlying data-sharing and C3I/C2IS grids like the Af-net can cost up to 4-5 billion dollars to develop and perhaps half of that to try and buy from some source.
So there is never any complete defense,but yes there are always ways to increase security in a relative manner and within the economic resources available.
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Zarvan is right when he states that an appreciable number of aircraft are required to allow vectoring with ground intercepts to be useful- which means that BD will require a much larger air-force than the one it maintains today- NOT 300 platforms- that's just hyperbole. Although in @
BDforever's defense- he was referring to SAM systems on naval platforms which do not usually work in concert with fighters- not at-least in the majority of the world's navies.