The Kaidai Type VI, also called the I-168 class, was built under the Maru 1 Programme and the Maru 2 Programme. They were faster than their predecessors, having the highest surface speed of any submarine in the world in the mid-1930s. However, their speed was surpassed slightly by later IJN submarines. | The Kaidai Type VI, also called the I-168 class, was built under the Maru 1 Programme and the Maru 2 Programme. They were faster than their predecessors, having the highest surface speed of any submarine in the world in the mid-1930s. However, their speed was surpassed slightly by later IJN submarines. |