Although movies, paintings, and stories often depict samurai wielding long-bladed katanas, the truth is that samurai used a wide range of weapons. They were proficient with longbows, spears, and eventually even guns. But what about the kunai?
Samurai didn’t use the kunai, or if they did, it wasn’t a weapon for which they were famous. Ninjas sometimes used the kunai, but it was actually more of a tool than a weapon.
The rest of this article will outline the types of weapons – particularly knives – that samurai used in battle. It will also explain the difference between the kunai and the katana. Finally, it’ll discuss the true intended use of a kunai and why ninjas were more likely to use them.
Also see Did Samurai Use Guns? to learn more.
What Kind of Knives Did Samurai Use?
Samurai had six main blades that they used for different things. The most famous of these was the katana. The samurai’s other blades were the tantō, kaiken, wakizashi, odachi, and tachi. The tantō and kaiken were daggers; the katana and the other three blades were types of Japanese swords.
The following is a breakdown of these six different blades:
Easily the most recognizable samurai blade, the curve-bladed katana is one of the least-used samurai weapons. It became famous primarily thanks to movies and artistic depictions of samurai fighting with it. However, these elite warriors were much more likely to use longbows or spears – ranged weapons – because they usually fought on horseback. 
Using a katana or another sword would have been impractical in most combat situations. Instead, katanas were largely ceremonial for the samurai. They did, however, become part of the official samurai uniform during the Edo (or Tokugawa) period. 
Most katanas range in length from 60 to 80 cm (23.62–31.5 in), are single-edged, and are used two-handed. (Some katanas can be wielded with only one hand.)
The wakizashi was a unique Japanese sword in that it didn’t have a standard length.  Instead, it could range from the size of a dagger to almost as long as a katana. Most were between 30 and 60 cm (12 and 24 in).
It’s curved and has a single edge, leading many people to call it a “shorter katana.” However, the weapons have different cross-sections, and smiths used a different method of forging them. In appearance, however, they do look very similar to a katana.
Also known as the nodachi, the odachi is quite similar to the more well-known claymore sword. Although it doesn’t have strict dimensions, most odachi were at least 90.9 cm (35.8 in) long.
Because of its size, the odachi could not fit comfortably on a samurai’s waist; some wore theirs on their backs, but that slowed them down when it was time to draw them. Instead, most simply carried these blades in their hands or had someone (similar to a squire) to hold them for them.
Tachi swords, too, are often confused with katanas, but the two are pretty different. The length of most tachi blades was between 70 and 80 cm (27 and 31.5 in), and they were also lighter than the katana in most cases.
The taper of the tachi was more severe, as was the curve, and the pointed end of the sword was smaller and sharper, which made the blade better for direct penetration.
Tantō were shorter, thinner, and lighter than any of the Japanese swords mentioned above. Samurai used them as a last resort in close combat settings if they were dismounted and forced to fight on foot.
Over time, the blades became less and less practical and more and more ornate until they were finally relegated to primarily ceremonial blades along with the katana.
Unlike the fancier tantō, the kaiken was a plain, unadorned dagger usually between 20 and 25 cm (8 and 10 in) long. Unlike many standard samurai weapons, kaiken saw use from both men and women, who’d secret them in their sleeves or a pocket of their kimonos.
They were very practical weapons used primarily for self-defense in close combat and stealthy situations.
Also see Did Samurai Katanas? to learn more.
What’s the Difference Between a Kunai and a Katana?
The kunai and katana are two very different things.
The kunai wasn’t actually a weapon; instead, it was a tool used much like a trowel for gardening or masonry. On the other hand, a katana was a weapon, even if samurai used it primarily for ceremonial purposes. Additionally, ninjas used kunai, whereas samurai used katanas.
As the saying goes, “anything can be a weapon if you use it correctly.” That was pretty much the philosophy behind the ninjas’ use of the kunai. As already mentioned, the kunai was a tool for gardening or masonry; some people used them as anchors or pitons. Others used them to dig holes into walls.
However, because the kunai had a sharpened point, ninjas also learned to use them in close combat situations. They were the perfect size, shape, and sharpness for stabbing and thrusting when close to an opponent.
Katanas, however, were long, curved blades that neither looked nor functioned like the kunai. Katanas had a longer reach and were better suited to slashing and cutting than thrusting and stabbing.
It’s also ironic that kunai were tools turned into weapons, whereas katanas were weapons turned into something used primarily for ritualistic or ceremonial purposes only.
Also see Did Samurai Use Spears? to learn more.
Did Samurai or Ninjas Use Kunai More?
Ninjas used kunai far more often than samurai, and there’s little evidence to suggest that samurai used them at all. All of the samurai’s main weapons were oversized ranged weapons that allowed them to fight from a distance while on horseback. The kunai would’ve been impractical for this purpose.
Conversely, ninjas were all about stealth and the up-close-and-personal kill. Shorter, sneakier, dagger-like weapons were optimal for that purpose. Ninjas also preferred lightweight weapons that they could easily conceal in their clothes, such as the shuriken. The kunai fit that requirement, as well.
Also see Did Samurai Use Bows and Arrows? to learn more.
Because samurai fought primarily on horseback, they preferred larger, ranged weapons. Kunai were tools, not weapons, but ninjas used them in combat anyway.