RE: Planetary defenses

>>	If a race lives in the atmosphere of a given planet, then that
race
>> is very vulnerable to space attack for the purpose of obliteration. 
All
>> that is required from an offensive force is to build devices that
will
>> destroy the atmosphere.  In case of the earth, a large number of
nukes
would
>> suffice to do the trick (think also about bio warfare). 
>
>No offence to nukes but you would need a LOT to make earth totally 
>uninhabitable. You'd need a fairly large number just to make the 
>majority of it difficult to inhabit. 
>
Or a few really big ones