A strategic location is a place that is important to conquer as an army because it gives you some kind of strategic bonus... such a thing would be like a hill because you can over look everything but I am talking about modern day military...
I personally think that hawaii (pearl harbor) and Alaska are the major strategic points of the united states...
okay, I got another scenario (and I am thinking of making a sort of club for this):
there are two main lands. One is yours and one is the enemies. On one there are mountains BUT there are a lot of marshes and the soil is bad and so not only is it hard to settle but it brings diseases and such... We will call it "mountainmarsh"
on the other mainland though, the ground is completely flat and even provides less sight of the enemy then just flat but it has a lot of life and materials. We will call it "flatisland"
note: remember, you are at war. Not at a settling age.
note #2: remember, without good resources and good life moral an army is weak
SO, would you rather be the empire that sits on "mountainmarsh" or on "flatisland"?
Defensively, the mountains. You could stage guerilla warfare, and It'd be hard to get tanks and trucks up there that could actually defeat you. It'd be hard to find you, and harder still for the enemy to move.
And sonic, how is it good for cannons? I rather shoot off people with a cannon from high ground then wait for them to get near me and possibly kill me...