What is “Economics of War’, gains & losses of a nation from economic & government standpoint.?

Answer 1

The gains are economic expansion and governmental expansion caused by the war. For example, more people are employed as people go to war, the government streamlines and improves tax collection to pay for the war, and industrial output generally increases.

The losses include the death of soldiers, munitions expended, losses of equipment (e.g. destroyed tanks, sunken ships), destruction of infrastructure (bridges blown, buildings destroyed), death of civilians, and the restriction of certain goods such as steel or food.