Quote Originally Posted by ganulv View Post
Terrain can be a multiplier, it is true. [1] [2]
Terrain is not the only item worth considering. Plataea and Marathon were won by better tactics and command. Nothwithstanding that, generally, a force using interior lines (like the Modocs in the lava beds, the Texicans in the Alamo, or any other force undergoing a seige) may be much smaller than its opponent and still be quite effective. And interior lines need not be on a small scale. The Germans had a similar advantage when they went on the defensive during the later parts of the European portions of both world wars. (As did they in Tunisia during the last of the WWII North African campaign.)

Interior lines can also provide an offensive advantage. Much as the Germans were able to shift forces back and forth between the Eastern and Western fronts during WWI to mount successive offensives, the US is naturally disposed to be able to use interior lines to shift between Atlantic-facing and Pacific-facing operations. This potential geographical advantage might be the basis for an argument for withdrawal from forward basing and downsizing, provided, of course, that US policy makers choose to eschew the Truman doctrine and return to something more like the Monroe Doctrine. But, as noted in Entropy's post, such a move would require revisiting/rewriting many currrent treaty obligations.