No.1-class minesweeper (1923)

The No.1 class minesweeper (第一号型掃海艇,) was a class of minesweepers of the Imperial Japanese Navy (IJN), serving during 1930s and World War II. 6 vessels were built in 1922-29 under the Eight-eight fleet plan. They have two sub classes, this article handles them collectively.

Background

 * In 1920, the IJN made Eight-eight fleet final plan, and they were going to have eight battleships and eight battle cruisers. However, they did not forget Hatsuse and Yashima in the Russo-Japanese War. The IJN was afraid that their new battleships was lost once again with an enemy's naval mine.
 * In the IJN, their destroyers undertook minesweeping operations. However, the IJN gave their destroyers a duty of minelayer. Therefore, they wanted the new minesweeper which could follow their new battleships.
 * The IJN demanded that they cleaned a route of the Combined Fleet by the No.1-class. Therefore, they gave No.1-class their destroyer and an equal weapons and 20 kt speed. Furthermore, the IJN more added a minelayer facilities for the No.1-class.

No.1 class

 * Project number I1. 4 vessels were built in 1922-1925. No.4 was behind with the laid down by the Washington Naval Treaty.

No.5 class

 * Project number I2. 2 vessels were built in 1928-1929. Improved model of the No.1-class. About their appearance, foremast was changed to tripod type.