The Imperial Japanese Navy developed the submarine faster than any other country in the world. But as a result of rivalries between the two military hierarchies, the Army and the Navy, they never utilised the submarine to its full extent. Nevertheless, during the Second World War, Japan deployed a number of unique submarines. These included the Type B1 which carried a Yokosuka E14Y1 reconnaissance seaplane in a watertight capsule attached to the deck of the submarine. One of these aircraft carried out two bomb attacks on a forest in Oregon by dropping six incendiary bombs, taking the war to the American mainland. The use of aircraft from submarines as scout planes proved not to be as successful as hoped, mainly because of the difficulty after launching the aircraft of it finding the submarine again in the vast Pacific and Indian Oceans. The Japanese also developed the giant I-400 class submarines that carried three Sieran bombers. There were other notable actions involving IJN