A manriki-kusari is a chain weapon, generally the length of the user’s arm, with balls of iron on either end. The name manriki-kusari translates as “power of ten thousand” to illustrate the weapon’s effectiveness.
The manriki was supposedly developed in late 1700s by a samurai named Masaki Dannoshin Toshimitsu as a way to kill without spilling bloodshed. Spilling blood on palace grounds and other sacred sites was considered sacrilegious. Masaki was head sentry at the main gate of Edo-jo (Tokyo castle).
The manriki has three main styles of attack. The first is to swing the chain circularly, letting the ends impact the body’s vulnerable targets with extreme force. The difficulty is in controlling the ends strike where you want while avoiding them bouncing off the target and hitting you. The second method is to strike blows with the hands holding the ends of iron so they smash into the enemy. When holding both ends of the chain in this way, the length of chain can be used defensively to block and entangle the opponent or it can be used to choke or throw the opponent. The manriki can also be thrown like a bolo.
A difficulty in facing the manriki (or any flexible/chain weapon) is the difficulty in blocking it, because although a parry to a sword stops the sword, a parry to a swing chain weapon just lets the end whip around the block to strike home. The manriki can also be used to entangle another’s weapon.
There is a book about the manriki – I thought it sucked.
This is a decent, non-embeddable video demonstrating differnet techniques.
This is actually a picture of Ascended Master William S. Burroughs’ manriki .
Another, more well-known chain weapon is the kusari-gama, which is a chain weapon attached to a sickle. The chain would be used to entangle an opponent from range while the sickle would finish them off upon closing.
Check out this kusari-gama & shinai fight!
Another, less well-known chain weapon is the Surujin or Suruchin – one of the traditional weapons of Okinawan Kobudo, which was historically a 6-9 foot rope with weight on the ends that evolved to be a chain with a weight on one end and a spike on the other. Some variants have a blade on the end (like the recent movie Ninja Assassin).
I actually always carry something similar to the surujin, which is basically a kubaton, a ~4 foot chain with a D-ring and heavy bolt at the end. I like to think of it as my “chain-sword”.