system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5- How was sword fighting an efficent way of combat in the old days?

Meaning, how did both parties not die from wounds inflicted during the fight 90% of the time? Or did they?

My thoughts come from modern fencing where the winner is the first one to touch the opponent (at least in epee) but is almost always still hit by the opponent.

Also the saying I've heard about knife fights, that the loser dies on the street, and the winner dies in the hospital.
gpt
It wasn't efficient, and AFAIK was never a primary means of combat in warfare. Swords and knives were the last ditch you used when you were too close in with the enemy to use anything else, or when you ran out of other weapons. The most popular weapons in history were probably some form of projectile such as a throwing spear, javelin, and bow along with the spears and halberds for non-ranged combat. Even famously sword-oriented warriors such as the samurai were first and foremost, bowmen. 

If you look at something like a Roman formation, they started with pilum (throwing spears), used pikes and spears between shield lines, and finally closed in and finished things up with the gladius (sword). 

The major historical exception to this occurs in the context of duels, which in fact often did lead to both parties being killed or maimed. Fencing for example, isn't a sport derived from warfare, but the tradition of Western European dueling.