Wakizashi is the generic name for Katana,the Japanese sword, with a blade
from 30 to 60 centimeters long.
Katana, the Japanese sword, which was originally used in actual battles,
was a head sword with a blade over 60 centimeters long,
and Wakizashi was used when Katana couldn’t be used because of damage or some other reasons.
Wakizashi mainly played a role of a spare, and it was actually not suitable
for two-weapon fighting much. It’s because a head sword was held by two hands,
and it was very difficult to handle it with one hand.
Wakizashi wasn’t a regular sword, and it was regarded as an ancillary equipment.
Therefore, people who weren’t Samurai, warriors, like peasants and merchants
were permitted to carry it with them.
For this reason, head swords called Nagawakisashi, long head swords, were used
in uprisings among gamblers.
Besides, when people felt it was unreasonable that they would be killed as executions for acting
disrespectfully to their masters, they were allowed to rise against them only with Wakizashi.
If the person who was a warrior was attacked and killed without resistance to it,
he was regarded as “inprudent” as a warrior who was in charge of the military and
constabulary power and his family was deprived of their rights as warriors and
their houses and belongings.
Thus, both of who would attack and who would be attacked had to face it at the risk their lives.
It sometimes happened that a boss instigated the person whom he tried to kill to turn
against him holding Wakizashi when he would attack the person, and he killed him with
a sword soon after that.
As for carrying two swords, long ones were popular in the end of Edo period,
and the letter written by Isami Kondo who was the top of Shinsengumi, a collection
of masterless samurai, says that the swords which had almost the same length
of head swords were good.
It is handed down as a secret in some persuasions with a style of classical
Japanese swordmanship involving use of two swords, they throw Wakizashi
from outside of the space between them and enemies and get close to the enemies
and attack with swords while they deal with the thrown swords.