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|Born||3 January 1909
|Died||26 July 1941
|Service/branch||Regia Marina (Italian Royal Navy)|
|Years of service||? - 1941|
|Unit||Decima Flottiglia MAS|
World War II
|Awards||Gold Medal for Military Honor (posthumous)|
Major Teseo Tesei (3 January 1909 in Elba – 26 July 1941 in Malta) was an Italian naval officer, who invented the human torpedo (called "Maiale", the Italian for "pig") used by the Regia Marina during World War II.
Teseo Tesei was born in Marina de Campo, Elba in 1909, the son of Ulisse Tesey and Rosa Carassale. After attending the Collegio degli Scolopi in Florence, he entered the Livorno Naval Academy in 1931, where he distinguished himself for perseverance and inventiveness. He was commissioned as a lieutenant and graduated from the Naval engineering school in Naples in 1933. He subsequently had several posts on both surface ships and submarines. He was a volunteer in the Spanish Civil War with the rank of Captain.
In 1929: Teseo Tesei had the idea of the manned torpedo, from the Italian device used to sink the Austrian Battleship Viribus Unitis during World War I, and invented for the Italian Regia Marina what was later called the Maiale.
- In 1931: He entered the Naval Academy of Livorno, where he showed his inventive capabilities. Together with Elios Toschi he designed a human torpedo called Siluro a lenta corsa (SLC), later nicknamed the Maiale (Italian for "pig", because it proved to be difficult to steer).
- 1936: He improved the attack performance of his creation, the "Maiale", using an enhanced system (that he invented) to breathe under water for two hours. The SLC was extensively used in World War II by the Italian Navy, and obtained even the sinking  of two British battleships in Alexandria. The British developed another kind of manned torpedo, called a "Chariot", from one of his captured "Maiali".
- 1938: He was one of the officers with Prince Valerio Borghese who organized the Decima Flottiglia MAS.
- 21 August 1940: Tesei was the only survivor when the Italian submarine Iride was sunk (see Decima Flottiglia MAS#1940).
- 26 July 1941: Tesei died riding a manned torpedo attacking Malta (see Decima Flottiglia MAS#1941). Teseo Tesei was posthumously awarded the Italian Gold Medal for Military Honor for this military action.
The modern Italian commando frogmen group COMSUBIN (Comando Raggruppamento Subacquei ed Incursori Teseo Tesei) is named after him.