The military is now the arm of an economic system rather than a political or ideological one.
Armies have a long and proud history of fighting for economic reasons. Personally, I cannot be arsed with an in-depth search of the historical record, but off the top of my head: conquistadors, Lebensraum, the Raj, Nazi gold.
Pretty much all exploration has had, at its roots, the search for lucre at its core. And where's there's lucre there's fighting. And when the lucre and fighting get serious enough there's armies.
Now the fighting is over black gold (or the fight against terrorism, which is less economic perhaps and more ideological). But before that is was gold gold, spices, whatever.
Yes, armies will fight over ideology and politics also, but to divorce those from economics is, in many/most cases, naive. Sorry, I said it!