It is not that conventional warfare is a simple thing and economic warfare is a complicated one; only that these forms of warfare have different sets of dynamics and considerations, but they do also tend to beget one another.
The victorious power that emerges as hegemon out of a general condition of conventional warfare may come out with some loftier ideals and a desire for peace, especially after a long period of instability and strife, and that power may have the means to bring some of that about in its domain, but that basic antagonistic instinct towards the Other never quite goes away.
There is a constant drive to expand, seeking out further security and stability, pacifying and homogenizing difference to make it predictable and controllable, and as the hegemonic power decays that drive becomes less "soft" and less "benevolent" and presses its subjects further up against the wall than they're already accustomed to, eventually creating the conditions for conventional warfare to break out again.
