[headsonpikes]

To the best of my knowledge, Mahan devoted his career to the study of naval warfare, not land fortifications.

Your general point about mobility is correct - read Mahan to see his insights about mobility and fighting ships.

[Freelance Warrior]

I think I must apologise for a misleading post. The Mahan I've posted a link about was the father (Dennis Hart) of the Mahan that Headsonpikes meant: Alfred Thayer Mahan, an US naval theorist.