Born in Piedmont in 1888, Antonio Legnani entered the Naval Academy in Leghorn in 1905. After graduating as an ensign in 1908, he served for a few years on battleships and cruisers, and in 1911-1912 he participated in the Italo-Turkish War as a sub-lieutenant aboard the hydrographic survey ship "Staffetta", in Red Sea. During this war, Legnani was promoted to lieutenant and appointed executive officer of the gunboat "Giuliana".