A Neoclassic of the Nippon Empire’s Naval Niceties

During the Second World War, the Imperial Japanese Navy had the most diversified fleet of submarines. It is worth knowing that the underwater fighters were grouped into various categories, such as manned torpedoes, midget subs, medium range subs, purpose-built supply subs, fleet subs, etc. 

The Japanese possessed submarines that had: the highest underwater speeds, the capacity to transport numerous bombers (the Sentoku I-400, which is renowned for being the largest submarine in the WW-II). They were armed with the finest and the most advanced torpedo of the war, the oxy-fuelled Type 95. It is noteworthy that, it is a plane that took off from one of these submarines conducted the only ever aerial bombing of USA.

Then why did Japan not succeed in intimidating and triumphing over her enemies? The answer is that, in spite of being technically advanced, the submarines were perilously few in number and their armaments did not match the technical sophistications of her enemies’.

Of all the submarines that the Imperial Japanese Navy possesse, the Sentaka type of undersea warriors was the finest model of submarines under the Nippon Empire which maintained a balance in the Pacific region during World War-II. The christening of the subs as “Sentaka” stemmed from “Sen”, which is an abbreviation for “Sensuikan” (Japanese for submarine) and “Taka”, a synonym of “Kosoku”, meaning high speed.

The Sentakas were monstrous weighing about 1070 tons, swam at a depth of 360 feet (approximately 110 m), and were armed with four torpedo tubes and 25 mm guns in sheathable pedestals to uphold streamlining. They were extremely powerful, agile with a capacious battery slot of two 2,500hp (approx. 1,900 kW) motors that powered the high-performing boats, which vaunted of streamlined all-wielded hulls. It is remarkable that their powers were nearly twice the horsepower of the German MAN diesels. The subs clocked an underwater velocity of 19 knots, about 35 km/h, which is more than twice the slowpoke submarines of America’s Navy. Like the later generations of the German U-boats, they were also equipped with snorkels that helped the submarine breathe for its fuel, diesel, while recharging batteries underwater.

The salient design features of the Sentaka include the unique single-hull structure, location of the main ballast tank higher than the previous versions to give a higher center of gravity thereby improving dynamic stability, a streamlined structure of the pressure hull and the casing, steel plates instead of wood for the upper deck, fitting of large horizontal fins at the stern, etc.

An interesting fact is that while the Germans called their subs U-boats the Japanese called them I-boats, though the exact reason for the same is unknown (probably stemming from Intelligent-boats, given their sophistications).

Twenty three boats were ordered but due to various constraints, only eight ships of the category “Sentaka” were commissioned, and of those only three, I-201, I-202 and the I-203 were built. Sadly, none of them were operated before the end of the war. However, the US Navy seized the I-201 and I-203, more so due to fear of Russian seizure of them than for scrutiny, before torpedoing them with their own submarines off the shores of Hawaii on May 21st and 23rd of 1946. The shards of the I-201 were found in 2009 by the Hawaii Undersea Research laboratory. What a waste of technological fineness!