Humanity’s ability to wage war has increased over time because you can now send millions to war without sacrificing food production.
We now live in a time where most of the countries aren’t at war most of the time. Before modern times, war was a constant state globally, but most nations could only afford to send a couple thousand people to war, and most battles were fought on fields, not inside cities, so even if your nation was in conflict with others during your whole life, chances were most wouldn’t be directly affected. You’d just till your fields like normal and at some points a different king would collect your taxes.