The Unit bears the name of the Roman leader Caio Duilio who, in 260 B.C. when Consul of Rome, in order to resist the powerful Carthaginian enemy fleet, created a fleet of 120 ships equipped with a hooked draw bridge – called crow, to exploit the Romans’ predominant tactic skills in grapple.
That same year the Roman and the Carthaginian fleet clashed in the Milazzo battle, where the Carthaginian were heavily defeated. Thanks to this victory, the Romans became the new rulers of the Western Mediterranean. Caio Duilio was the first Roman to triumph in a naval battle and a column made with the rostra of the enemy ship was erected to celebrate his victory. The same column with rostra now shows in the Crest of the Unit.

Destroyer Caio Duilio is the fourth Unit in the Italian Navy to bear this heroic name. The first unit was a dreadnought in service between 1880 and 1909.
When first launched, thanks to her 450mm cannons, she was considered one of the most powerful battleships of her times. Although never employed in battle, she contributed to the international recognition of the newborn Unified Italy.
The second unit was a battleship launched in 1913 and modernized in 1937. This Unit took part in World Wars I and II and was operational until 1956, thus becoming the first flag ship of the newborn Republican Italian Navy .

The third unit, a guided missile cruiser, was launched in 1960 and operated until 1990. She was the first vessel of her kind to be built in Italy after the war. In her last operative years she was used also as school ship cruising between the two coasts of the United States during the Los Angeles Olympic Games in 1984, along Latin America in 1987, together with two Maestrale class frigates, and in Australia in 1988 during the 1988 Australia's Bicentenary celebrations.

The current Destroyer Caio Duilio was launched on October 23, 2007; a few days later was moved to the Muggiano (SP) Shipyards to be fitted with a combat system. On February 12, 2008, she performed her first sea trial and was delivered to the Italian Navy on April 3, 2009. On May 5, in La Spezia, together with her sister unit Andrea Doria, and the French units Forbin and Chevalier Paul, she performed a joint exercise which involved all the Orizzonte class units.
On June 10, 2010, she took part in the Naples Navy parade, and in 2011 in La Spezia.
In February 2011 she participated in the NATO Proud Manta exercise in the Ionian Sea, together with other units, submarines and aircraft from 9 different allied Nations. On September 22 the same year, she was given the combat flag in Gaeta (LT).
In 2012, after passing the tests for the Anti Air Missile System (PAAMS), she has been recognized “Combat Ready” and has participated in the national Mare Aperto/Amphex exercise, proving the efficiency of her new sensor and weapon systems.
In the beginning of 2013, she was part of the naval group which carried out presence, surveillance and cooperation operations jointly with other coastal Countries and was active in the Mediterranean Dialogue in the Eastern Mediterranean Sea.
The motto of ITS Caio Duilio is a reference to the ancient Roman tradition according to which the name has a religious meaning. “Nomen Numen” can be translated into: “the Name means Power:” and it probably refers to mighty Caio Duilio.
In the lower part of the Crest is the stylized relief silhouette of the Unit with the pennant (D554). In the upper section is Caio Duilio’s rostral column (Columna Rostrata C. Duilii).
In the upper part of the Crest is a towered crown, beneath which, between two five-pointed stars, is the ship’s motto.