Japan's combat experience in the Solomon Islands in 1942 which revealed the difficulty of resupplying Japanese forces in such situations prompted the IJN to commence an amphibious tractor program in 1943, as the Ka-Tsu,[3] which was designed by Commander Hori Motoyoshi of the Kure Naval Yard.

The Ka-Tsu's primary purpose was to transport cargo and/or troops ashore.

[1] Its engine compartment and electric final drives were hermetically sealed, as it was intended to be launched from a submarine.

[3] The twin drive propeller shafts were designed to retract "into their ducts" once the vehicle reached the beach.

It was proposed that a Ka-Tsu armed with a pair of naval Type 93 torpedoes[4] be dropped off by submarine away from the atoll, propel itself to the outer reef using its tracks, and then enter the lagoon on the inside of the reef.