Nanban trade
In the 16th century Japan began trading with Europe during what would become known as the Nanban trade. Samurai acquired European cuirasses which they modified and combined with domestic armour as it provided better protection from the newly introduced matchlock muskets known as Teppo or from the Portuguese trading Post in the town of the same name. The introduction of the "Teppo" in 1543 along with a change in battle tactics caused armourers to change the design of the "dō" from the centuries-old "lamellar armours" to "plate armour" constructed from iron and steel plates. This type of armour was called "tosei gusoku" (new armours). Bullet resistant dō were developed, this type of armour was called (bullet tested) allowing Samurai to continue wearing their armour despite the increasing use of firearms.