​He was born on 7^th February 1909 of a noble family from Piedmont and Capua. He attended the Military Academy of Modena until 1931, taking the rank of First Lieutenant of the Royal Army Cavalry. Assigned to the regiment "Monferrato Cavalrymen", he showed his military qualities especially as cavalryman. He was one of the first Officers of the Italian Cavalry that adopted the natural riding method of the Captain Federico Caprilli; for his innate equestrian abilities he was included among the four cavalrymen that would have constituted the Italian riding team for the Berlin Olympics in 1936. However, he never arrived to the Berlin Olympics because the Abyssinia campaign started and the Lieutenant Guillet did not hesitate to participate: his military duty was to serve the Nation and the war campaign took priority.

Assigned to the Royal Corp of the Colonial Troopers, he served in Libya at the Spahis unit and in October 1935 he commanded a platoon during the first war actions in Ethiopia. On 24^th December of the same year he was seriously wounded to the left hand during the battle of Selaclaclà. When the hostilities ended, on 5^th May 1936, he was awarded in Tripoli by the Marshal of Italy Italo Balbo for his exemplar and courageous attitude in war.

In August 1937 he accepted the proposal of the General Frusci to follow him in the Spanish civil war, where he had the chance to distinguish himself in the battles of Santander and Teruel; there he commanded a tank unit of the division "Fiamme Nere" (Dark Flames) and headed a Moroccan cavalry tabor. After a short period of convalescence in Italy, he was moved to Libya as 7^thSavari squadron Commander.

Just before Italy entered into the World War II, Guillet was sent to Eritrea and appointed Commander of the Gruppo Bande Amhara, a multiethnic military unit, with 1 700 Ethiopian, Eritrean and Yemeni men. The Guillet's Group had to operate, with autonomy and freedom of action, against the enemy in the north-western of Eritrea.

In 1939, during a battle against the guerrilla in the region of DougurDubà, the Lieutenant Colonel forced the enemy to a fight in open field. During one of the attacks his horse was hit and killed.

Immediately Guilletwanted another horse; when also the second horse was hit he took command of a machine gun and shot to the last rebels on the battlefield. For that action, "worthy example of heroism and contempt of danger", he was awarded with the Silver Medal to the Military Valour. He was nicknamed "Devil Commander" by his native soldiers because they were convinced that he was immortal. The night of 20^th January 1941, Guillet came back to the Cheru fort after a long and exhausting patrol activity but he had to leave again to face the English Gazelle Force that threatened to encircle thousands of Italian soldiers retreating towards Agordat.

At the dawn of 21^st January the Guillet's Group, armed with swards. Guns and grenades, attacked the enemy from behind by creating confusion among the Anglo-Indian ranks. After having passed unharmed among the enemy troops, the Group returned on their initial positions to attack again. That was the last cavalry assault in the military history of Africa.

Guillet headed also his Group in the battles of Cochen and Teclesan but they were defeated in Asmara on 1^st April 1941.

After the defeat in Asmara, Guillet realized that the only way to help the Italian troops on the northern-African front was to keep engaged the English soldiers in Eritrea. On 3^rd 1941, Guillet decided that, if Rome had ordered the surrender he would have continued the war against the English soldiers in the Eastern-Africa. He gathered about a hundred of his native soldiers and started a violent guerrilla against the English troops. His legend grew and the English intelligence started a "manhunt". It was also established a reward of more than a thousand pounds of gold; but Guillet was never betrayed, neither by the tribal leaders previously in war against the Italians that offered him a refuge. During the guerrilla, for almost eight months he assaulted and plundered English deposits and trains, he blew up their bridges and tunnels making unsafe the communication routes. However, at the end of October 1941, his ranks were reduced and so the aim of his mission was no longer attainable. In particular, the capture of his grey horse Sandor by the Major Max Harari of the English intelligence, that was responsible for the Guillet's research, it made him realize that he could not continue the war. So he gathered his Group, thanked them promising that Italy would have rewarded them and went away.

Guilletsettled in the outskirts of Massaua where he assumed the false identity of Ahmed Abdallah al-Redai, Yemenite worker. He transformed himself  into an authentic Arab in order to remedy in Yemen.

After having reached Yemen, he became groom in the guard of the Imam Yahiah, the Yemenite King. The Imam gave Guillet the rank of "Great Maniscalco of Court" and he appointed him as tutor of his children. Guillet became also responsible and instructor of the Yemenite horse guards and passed more than one year at the court by revealing his history to the Imam. In June 1943 he embarked on a ship of the Italian Red Cross and after almost two months the Captain arrived to Rome on 3^rd September 1943.

He was promoted to Major for war merits and then he asked for money, men and weapons to come back to the Horn of Africa and resume the clandestine war against the Allies. However, times had changed: the language knowledge and the experience permitted to Guillet to be assigned to the Military Information Service and employed in dangerous missions in Italy that was occupied by the Anglo-American troops. The armistice of 8^th September was a surprise for him; he crossed immediately the Gustav line and arrived to Brindisi to be at the disposal of the King. In September 1944 he married his beloved Beatrice Gandolfo in Naples. He continued to operate for the Secret Service of the Italian Army and since 25^th April 1945 he became a Secret Agent. It was in that position that he could recover the imperial crown of the Ethiopian Negus, stealing it to the "Garibaldi" Brigade that had confiscated it to the Republic of Salò. The crown was then given back to the Negus and it represented the first signal of reconciliation between Italy and Ethiopia.

At the end of the hostilities, after the defeat of the Monarchy and the victory of the Republic at the Referendum of 1946, Guillet remained faithful to his military oath towards the Savoy Crown and resigned from the Italian Army.

Guillet graduated in Political Science and in 1947 he won the competitive exam for the diplomatic career. In 1950 he was assigned to the Embassy of Cairo as Secretary of Legation. In 1954 he was appointed Business Officer in Yemen (where the Imam's son welcomed him warmly saying: "Ahmed, you have finally come home!"); in 1962 he was appointed Ambassador in Amman where the King Hussein of Jordan used to ride along with him (the King named him "uncle" that in the Arab culture is an expression of respect and familiarity).

In 1967 is Ambassador in Morocco. During an official reception, involved in a shoot caused by an attempt of coup d'état, he managed to save diplomatic representatives. The Federal Republic of Germany awarded him with the Grand Cross with star and strip of the Order of Merit of the Republic. In 1971 he was sent to India as Italian Ambassador and he entered the entourage of the confidants of the Prime Minister Indira Gandhi. In 1975 he concluded his diplomatic carrier.  ​

In 2000 he followed the writer Sebastian O'Kelly in Eritrea, in the places where he operated with his Amhara Group. He was received in Asmara by the President of the Republic with the honours​ reserved for Heads of State.

On 20^th June 2000 he was awarded with the honorary citizenship of the city of Capua that he defined "highly desired".

On 2^nd November 2000, the President of the Republic Carlo Azeglio Ciampi awarded Amedeo Guillet with the Grand Cross of the Military Order of Italy that is the highest military decoration in Italy.

The Devil Commander died in Rome on 16^th June 2010 when he was 101 years old.

On 26th 2010 the Archbishop Bruno Schettino celebrated the funeral in the Cathedral of Capua. His remains are in the family grave, next to his wife Bice and his ancestors that had moved to Capua after the annexation of the Savoy by France.