Okay, so a long, long time ago, when people lived in tribes and wore animal skins for clothes, sometimes there were battles between different tribes. And guess what? Women fought in those battles too!
In ancient times, people didn't really care if you were a boy or a girl when it came to fighting. As long as you were strong enough to hold a weapon and defend your tribe, you could be a warrior.
For example, in ancient Egypt, there were women who fought as archers and charioteers. They were called "vanguard" or "forward" women, because they were the first to charge into battle.
In China, there were also female warriors, like the legendary Mulan. She dressed up as a man and went to war in place of her father.
In ancient Greece, women were not allowed to fight in battles, but they did play important roles as priestesses and leaders. Some even led armies, like Queen Artemisia of Halicarnassus who fought against the Greeks in the Persian Wars.
As time went on, women's roles in warfare changed. People started to think that women should stay at home and take care of the family, while men went out and fought wars. But even then, there were still women who disguised themselves as men to fight in battles.
It wasn't until the 20th century that women were officially allowed to serve in the military in most countries. But even still, there are some people who don't think women should be soldiers.
So, in summary, a long time ago, women fought in battles just like men did. Some were archers or charioteers, some were leaders, and some even disguised themselves as men to fight. As time went on, women's roles in warfare changed but there are still women who serve in the military today.