I think the parent is talking just about economics. There are very few post-industrial-revolution examples of nations benefiting economically from war. America in WWII is the most notable exception in my mind.
In spite of my flippant tone, I had a serious point too: fighting a war may always come with an economic cost, but losing one can come a much higher cost. Hence, fighting a war can be a positive choice even if you lose money doing it.
That's really interesting. To put it another way, economic opportunity costs apply to armed conflict.
You can even extend this beyond purely defensive wars.
The most obvious extension is pre-emptive wars. A great example would be the Six Days war (aka the 1967 Arab-Israeli war). Israel knew that they were about to be attacked (the massed units on their borders were not subtle), and instead attacked preemptively. Arguably, this reduced the cost of the war for them in a number of ways. First, by seizing the initiative and the element of surprise, they likely reduced their combat losses relative to what they would have experienced if they had waited for their neighbors to attack. Even more importantly, the entire war was fought outside of their then-borders, so their infrastructure was not damaged by the fighting.
Clausewitz even makes a case for starting a war that you know you are going to lose. That sounds crazy at first, but in some scenarios it makes sense, because it's not just about the balance of power, it's about the direction in which that balance is shifting. If you are highly certain that another country is going to attack you, and that you will lose, you have to consider whether your defeat would be more or less severe in six months or a year. If the balance of power is shifting in your favor, you want to postpone hostilities as long as possible. If, on the other hand, the balance of power is shifting in favor of your enemy, you want to precipitate a war as soon as possible in the hopes of securing a better position to sue for peace. Either way you know you're going to lose, it's a question of how badly you are going to lose.
Finally, even a war of naked aggression could have a nearly immediate net positive impact on your economy if your forces are so superior that you will suffer minimal losses, and if you capture valuable resources as a result, or if you secure tactically valuable terrain that reduces your losses in an impending conflict. The German annexation of the Sudetenland is a prime example of this.
>As much as you might like to think differently war is alway negatively productive.
I never suggested that war has a positive influence on an economy, so I'm not sure where you got that impression. I was suggesting that one political party or the other might want to use war as an excuse for deficit spending to further their political agendas.
That being said, war can be positively productive if you are outside of it, selling to one or more of the belligerents. That's mainly how WWII was so positive for the U.S. economy: we were selling to the allies for several years before we got directly involved. The Russians made plenty of money selling to both sides of the Iran/Iraq war, and I'm sure that those are just two of many, many examples throughout history.
There might be some corner cases where the destroyed wealth is replaced by more efficient use, but they have yet to demonstrate themselves.