When it comes to famous samurai clans and legendary sword battles, Japan’s history is full of them. From Sasaki Kojiro and his famous duel with Miyamoto Musashi to tales of Uesugi Kenshin and Takeda Shingen, these battles are dramatic and compelling. While there are many standout warriors throughout Japan’s samurai history, there is one who was considered to have the deadliest sword. 
The Katana of Masamune
Many people acknowledge that Masamune was Japan’s greatest swordsmith. Gorō Nyūdō Masamune was active around the 13th century, when samurai warriors were in a constant sword battle, and this style of weapon was in high demand.
In addition to being a very talented smith, Masamune also understood the mechanics of the samurai fighting style as well as their needs when battling their most fearsome enemy — the Mongols. He actually developed the katana from the common swords of the period, like tachi and kissaki.
His work was based on the work of a previous swordsmith named Amakuni. Many legends talk about the frustration Amakuni experienced watching his swords break during battle after battle.
He began experimenting with different materials and blade shapes until he found one that could stand against the armor and weapons of the enemy. He created his deadliest sword, the tachi, which Masamune then transformed into the katana.
His Katanas
The katana has a slender design with a curve in the center that soldiers could effectively use for slashing and stabbing. Masamune’s katana creations were more than just the deadliest swords around, they were also incredibly beautiful. His weapons quickly became the benchmark for all samurai weapons, and the katana transitioned into a position as a samurai’s most important weapon.
An old portrait of Masamune
Masamune’s Weapons History
Many of Masamune’s creations were considered some of the deadliest swords available, but there are some more famous than others. The most infamous sword he created is called the Honjō Masamune katana. This sword has been passed down by shōguns throughout the centuries until it arrived in the hands of Tokugawa Iemasa — its final owner.
This sword was named a national treasure in 1939 but disappeared in the midst of World War II. After the war, someone surrendered it to a police station under laws imposed by the American occupation. Since nobody recognized the world’s most infamous and deadliest sword, nobody knows what happened to it or where it went.