According to history, the oldest description of Damascus steel swords could date back to 540 A.D., although there is no precise evidence and it has been said that they may have arisen much earlier.
Damascus steel is based on a type of steel manufactured in India, which then spread across the world until it reached Damascus. The large numbers of swordsmiths working in the capital of Syria expanded the ways of manufacturing Damascus steel, managing to create a durable, unbreakable, type of steel. Thus, arose Damascus steel, also known as damascened steel.
The swordsmiths of Toledo have always worked closely with those of Damascus, so the masters in Toledo researched the composition of damascened steel, its beautiful iridescent marbled surfaces, and its quality of being strong without breaking or bending. Based on the results attained, they realised that it was precisely the marbling on the blades that made Damascus steel so high-quality. Along a similar line, we must remember that the waters of the Tagus River are also believed to have extraordinary properties that give the swords and knives of Toledo their special quality: the sands, where the key to this quality is said to lie.
This is how the best swords in the world are forged and tempered.