In 1916, as a part of the development of the fleet, the Japanese parliament approved the construction of two battlecruisers in addition to the Kongō-class ships. That same year, Japanese shipbuilders presented four battlecruiser projects that differed in the power of the propulsion unit and individual armor elements but were all capable of reaching a speed of 35 knots. The six-shaft power unit became a specific feature. After a number of improvements, these designs became the basis for the Amagi-class battlecruisers.