I don't think that's true. At all point of history, fortifications have never been more than a force multiplier for the garrison manning the fortifications. Se

I don't think that's true. At all point of history, fortifications have never been more than a force multiplier for the garrison manning the fortifications. Send an overwhelming force at it and it will always fall (I don't know what kind of impregnable modern fortification you have in mind but I'd be curious to hear what you have in mind) but it requires the effort and ability to send such an overwhelming force. Even in the battle of France, famous for the failure of the Maginot line to stop the Germans (mostly because of a Franco-Belgian political dispute in the 30s, by the way), the Italians were completely unable to get through the fortifications in the Alps despite a massive numerical superiority because they were tactically inept.