How did nations include the entire population to win the war?

A population of a country can be controlled by war. During the war, there's a high death rate and low birth rate which decreases the population drastically, however post war there will be low death rate and high birth rate which increases the population.

Explanation:

it makes companies more competitive it mainly alot

giving the us more money to give to the states it allows them to sell oversee and to other countries and more

d. the right to establish a one-house legislature