It is true that war is not exclusively an economic activity - after all, there was a school of thought that with the economies of Europe doing so well in the first decade of the 1900's, and with modern militaries (particularly navies) being so expensive, nobody would want to kill the fiduciary goose laying all those golden eggs by embroiling Europe into a continent-wide war. Bismarck knew better, and said that if war came, it would be due to the actions of "some damn fool in the Balkans". He turned out to be right. Better yet, read how accurately Engels (yes, the communist) described what would happen in the next war.
That being said, while logistics and economics by no means guarantee victory, they do place constraints on what can and can't be built, fielded, and effectively supplied...and what kinds of units will provide steadily-diminishing returns.
