Samurai armor, known as "yoroi," was designed to provide protection to samurai warriors on the battlefield. It consisted of several layers of protective elements, including metal plates (such as iron or steel) laced together with leather or silk cords, and was often supplemented with other materials like leather, silk, or cloth. The armor covered the samurai's body, including the torso, arms, and legs.

While samurai armor was effective in providing protection against various types of attacks, including arrows, spears, and blunt force, it had limitations against the cutting power of a well-made and properly wielded katana. Samurai armor was designed to distribute the force of a blow and deflect or absorb impacts, rather than completely stopping or neutralizing them.

The surface of the armor had various elements to enhance its protective capabilities. It had raised ridges and overlapping plates that could help to dissipate the force of a blow and deflect sword strikes. Additionally, the armor's construction allowed for mobility and flexibility, enabling the samurai to move and fight effectively.

However, a well-crafted and sharp katana could still find vulnerabilities in the armor. The katana's curved blade was designed to concentrate force on a smaller area, making it effective at cutting through or penetrating armor. Samurai warriors would aim for weak points in the armor, such as the gaps between plates, joints, or areas with less protective coverage.

To further enhance protection, samurai warriors sometimes wore additional layers underneath their armor, such as padded garments or chainmail, to mitigate the impact and penetration of blade strikes.

Overall, while samurai armor provided a degree of protection against katana strikes, it was not impervious to the cutting power of the sword. The effectiveness of the armor depended on various factors, including the quality of the armor, the sharpness and technique of the katana, and the skill of the samurai wielding it.