There are many different versions of the Bassai Kata in the various styles of karate, but historical evidence found by many historians have come to the conclusion that Bassai Sho can be credited to Master Itosu.
Bassai Dai can be described as ‘To storm a fortress’, whereas Bassai Sho can be described as ‘to storm a fortress and capture the enemy', with the former being the break into the castle, and the latter being the escape. When you apply these mental attitudes to the Kata, performance is both intense and emotionally charged.
Seemingly lighter than Dai, this kata uses less brute force, and more dynamic movements in order to generate power. The only contradiction being at the kiai points in both kata, where in Dai, you lightly support the right hand, whereas in Sho you forcefully hold the arm that grabs at the hair, wrist, or lapel of the gi.
One element of this kata that is particularly useful is the defence against a stick attack, with the applications being of great interest.
Although this kata does not look as powerful as Dai in appearances, you may find that there is a dangerous calm to this kata, with techniques such as the end movements being particularly dangerous, although visually they appear very graceful and beautiful.