To many, the longsword is considered to be the pinnacle of European swordsmanship; coming at the end of the sword and shield era when full plate armor was being invented and started to be widely used, the need for a shield was quickly diminishing, simultaneously smiths around Europe were making breakthroughs in making stronger metals that were able to be lighter and longer without becoming either too heavy to be useful, or too weak to sustain long combat. The longsword was invented to be the perfect middle ground between the one-handed(arming) sword, and the large two-handed swords that were used in war. Light enough to be used in one hand to free the other hand for shield use if necessary, or for grappling the opponent, and with long enough handles to be used in two hands for strength, speed, and accuracy. These weapons were considered to be the most chivalrous option available and were constantly used in duels of honor and to defend your life while unarmored.
Because of the multitude of ways this weapon could be used it is shown in both armored and unarmored usage, on horseback, and in purely self-defense scenarios. The vast majority of manuscripts we have found detail the use of the longsword at least in part, and it is absolutely the most well documented of all the Historical European martial forms.