I see this that lets go to war means let us ulter the existence of certain economic progression. Apart from death of people both soldiers and the civilian, it take back the system backward from the party in the war but the effect is more on the people not in the fighting, the world at large. It is effect more on the world as it increase inflation and reduce the living of the people of the world if the countries have major contribution for the world economy.
The effect of war include rising inflation, extreme poverty, increasing food insecurity, deglobalization, and worsening environmental degradation. All the effect here are what we see in the Ukraine and Russia war, example is inflation that is affecting different country in their economy because products going out from Ukraine like wheat or corn leaving out there in small quantity and expensive. Russia is not supplying energy to Europe neighborhood and that slow access to production in the region there and causing life to be difficult.
Russia is a major supplier of fossil fuels, especially to Europe. Disruptions to supplies of these commodities are driving up prices.
The degradation of environment is also there if war happen and this is major effect on agricultural produce leading into the food shortage and insecurities around that.
There are many negative effect of war but no profit and
rebalancing fiscal priorities could prove quite challenging even in advanced economies.