Before the emergence of the katana, the primary sword used by samurai in Japan was the tachi. The tachi was a longer, curved sword that predates the katana and was commonly used from around the 9th to the 15th century. The tachi was worn suspended from the samurai's waist, with the cutting edge facing downward, and was primarily used in cavalry warfare.

The tachi differed from the katana in a few key aspects. It had a longer blade, typically measuring around 70 to 80 centimeters (27 to 31 inches) in length, compared to the shorter katana. The curvature of the tachi's blade was also generally more pronounced. Another difference was in how they were worn—while the tachi was worn with the cutting edge down, the katana was worn with the cutting edge up.

The tachi's primary use was in battlefield combat, where samurai would engage in mounted warfare. Due to its longer length and curved design, the tachi was well-suited for powerful slashing attacks from horseback. Over time, as warfare and fighting styles evolved, the need for a more versatile and agile sword became apparent, leading to the development of the katana.

The katana, with its shorter length, enhanced control, and versatility, eventually surpassed the tachi in popularity during the Muromachi period (14th to 16th century). The katana became the iconic weapon of the samurai and was designed for both mounted and infantry combat. It represented a shift towards more refined techniques and closer-quarters fighting.