Understanding that most if not all of the posters here have as much knowledge of these things as both you and I, we seem to agree on the "theories" of this topic. In example, the Cheyenne Mountain Complex-or "static fortification". Some may not have been aware of the Airborne Command Post, (which incidentally was only removed from the 24/7 role it traditionally held throughout the 50's. 60's, 70's and 80's for cost reasons) amongst other "secret" activities that our Gov't feels/felt were/are necessary to protect America. Therefore I choose not to elaborate to extremes the vastness of the conversation. However, there was a time when some within the JCS or National Command structure felt that they were "nuke proof" or in essence "nuclear hardened"-as is the case for Cheyenne Mountain. Which can only be assumed to be the case in other countries like Russia or China. Entire systems were devoted to "cracking" the "nuclear hardened" sites. Massive resources were devoted to rendering these fortifications useless, or next to useless in the event of a Major Conflict-ones that included Nuclear weapons. As other posters and I are aware that our national policy was based on a "launch upon detection" stance, or more pointedly ie. a "use them or lose them" policy. Which incorporated the doctrine of MAD and protected America and her allies, and the free world for that matter, for close to 40+ years. However, the mission at Cheyenne Mountain has evolved into that of a Space Command and Control. I agree 100% with you, as others will, that, "The function of Cheyenne Mountain is to keep nuclear war from starting" as their role (traditionally) was that of detection, communication, and control. I may be sounding a bit long-winded here to make my point-which is that of the static fortification being rendered useless in a conflict; contrary to the original posters argument about the viability of a static fortification in Modern conflict.
To address your statement about the reliance upon precision-guided munitions, and being "oversold", perhaps as I had stated above, I was trying to be brief. To expand upon what we are discussing for the layman, or novice, I would incorporate what you have outlined (ie.-the Political Cost) as one reason for the move to Laser-Guided or GPS guided munitions. One of other reasons is a financial cost. If we were to go back and look at the tonnage dropped on Germany by the 8th AF in WW2, we learned that the number of tonnes dropped as compared to the percentage of tonnes dropped that actually HIT THE TARGET was miniscule. The CEP was in the 1/2 mile range. With advances in targeting computational power (Norden Bombsight) the allies were able in increase the accuracy of hitting their targets to within a few hundred yards. However, there was still the cost of the men, and planes which had to deal with the German AA defenses and the rapidly disappearing Luftwaffe. There was an enormous cost involved in producing those planes, training those men, moving the assets to England, building bases, etc., etc. As time and the industry advanced, and as computer power and technology advanced the idea moved to the rudimentary forms of precision munitions as seen in Vietnam-(which oddly saw a number of tonnes dropped which EXCEEDED that of all WW2). The bombers flew higher, the sorties vs. targets decreased (excluding vs Hanoi-please no arguments there) as the CEP shrank and shrank. Still dangerous tho. The idea of Stand-Off Weapons on a tactical level were just around the corner, as advances in rocketry, computing power, etc., were coming on-line. I would delve deeper into the theory as we approach Desert Shield/Storm, but that is moving this point away from the central argument of "static fortifications" and Modern Warfare.
Unfortunately, I need to disagree with you on some level, about the "They are effective but they are also very very expensive for the amount of damage they produce". It is true they are expensive for the amount of damage they may cause, but when weighed against the number of planes/pilots used/lost, or number of sorties flown vs. target destruction, etc., they are very cheap, highly accurate, (CEP of inches) minimize the political cost (Civilian casualties), improve battlefield strategy/tactics, yadda, yadda, yadda. I think why this is why our movement or reliance upon this munitions is at an all-time high-because of their cost-effectiveness. Therefore vs. static fortifications it is clear that no matter how "hardened" your fort is, there are weapons and or means of destroying them from the air/ground. Barring the complete deep burial needed in complexes such as Cheyenne Mountain, or Irans Nuclear sites. But I'm again, losing my point.
As for the last part, of the German Luftwaffes' adapting to to their enemies deterrents (a principle of Sun-Tzu), they built their Air Force to effectively deal with what they encountered which is why the relied upon the Junkers Ju-87/88 and the idea of Close Air Support (which was borne out of their adaptation of the new "technology" of air combat. They learned their lessons well, and soon succumbed to the students learning.
Lastly, it is still my contention that Modern Battlefields holding anything beyond basic fortifications-which were nicely outlined above by another poster-that include wire, trenches, berms, minefields, dragon teeth, or other anti-vehicle obstacles, natural and man-made geographical obstacles, etc., are just targets of opportunity waiting to be attacked. For every obstacle encountered-whether it is an "old" one, or one yet to be invented some MIC is working on destroying it even as I write this. Every Castle wall was breached or tunneled, rivers crossed, forests driven thru, mountains climbed or bypassed-WITHIN THE STRATEGIC GOALS of the overall Battle Plan.
Short of burrowing deep within the earth, which limits the offensive capability of that fortification, a fluid, mobile strike force of combined arms will overcome it like Joshua allegedly overcame the walls of Jericho.
