Dux in the context of Nikephoros Basilakes

The Albanian nobility was an elite hereditary ruling class in Albania, parts of the western Balkans and later in parts of the Ottoman world. The Albanian nobility was composed of landowners of vast areas, often in allegiance to states like the Byzantine Empire, various Serbian states, the Republic of Venice, the Ottoman Empire and the Kingdom of Naples in addition to the Albanian principalities. They often used Byzantine, Latin or Slavic titles, such as sebastokrator, despot, dux, conte and župan. Notably, they also constructed religious sites, castles and had powerful courts. The Albanian principalities were usually divided in history except during the Principality of Arbanon when there was only one Albanian state ruled by one dynasty, and also during the League of Lezhë where most of the Albanian nobility and peasant communities unified under a military alliance against the Ottoman Empire.

Paristrion (Greek: Παρίστριον, lit. 'beside the Ister'), or Paradounabon/Paradounabis (Παραδούναβον / Παραδούναβις), which is preferred in official documents, was a Byzantine province covering the southern bank of the Lower Danube (Moesia Inferior) in the 11th and 12th centuries.

Although Byzantine authors use the term to describe the lands along the Danube in general, the province of Paristrion seems to have comprised mostly modern Dobruja. It is not certain exactly when the province was established: the Romanian scholar Nicolae Bănescu considered that it was established immediately after the end of the Rus'–Byzantine War of 970–971, while others, such as Vasil Zlatarski, thought it a later, mid-11th century creation. It was governed by a katepano or a doux, and was probably based at Dorostolon (modern Silistra), where a Byzantine strategia ("generalcy") is indeed attested in the 970s. In the aftermath of his victory over the Rus', Emperor John I Tzimiskes (r. 969–976) appointed general Leo Sarakenopoulos as commander over north-eastern Bulgaria, based at Pereyaslavets/Ioannopolis. Sarakenopoulos and his subordinates engaged in major fortification activities in the region of the Dobruja over the next few years, where abandoned Roman-era forts were rebuilt and re-occupied.

The doge of Venice (/doʊdʒ/ DOHJ) – in Venetian, doxe de Venexia [ˈdoze de veˈnɛsja] – was the doge or highest role of authority within the Republic of Venice (697–1797). The word doge derives from the Latin dux, meaning 'leader', and Venetian for 'duke', highest official of the republic of Venice for over 1,000 years. In Italian, the cognate is duce (/duːtʃeɪ/ DOO-chay, Italian: [ˈduːt͡ʃe]), one of National Fascist Party leader Benito Mussolini's titles. The title is also cognate to the English "duke", with a different meaning.

Originally referring to any military leader, it became in the Late Roman Empire the title for a leader of an expeditionary force formed by detachments (vexillationes) from the frontier army (limitanei), separate from, but subject to, the governor of a province, authorized to conduct operations beyond provincial boundaries.

The Duchy of Rome (Latin: Ducatus Romanus; Greek: Δουκᾶτον Ῥώμης, romanized: Doukâton Rhṓmēs) was a state within the Byzantine Exarchate of Ravenna. Like other Byzantine states in Italy, it was ruled by an imperial functionary with the title of dux. The duchy often came into conflict with the Papacy over supremacy within Rome. After the founding of the Papal States in 756, the Duchy of Rome ceased to be an administrative unit and "dukes of Rome", appointed by the popes rather than emperors, are only rarely attested.

The Franks, Germanic peoples that invaded the Western Roman Empire in the 5th century, were first led by individuals called dukes and reguli. The earliest group of Franks that rose to prominence was the Salian Merovingians, who conquered most of Roman Gaul, as well as the Gaulish territory of the Visigothic Kingdom, following the Battle of Vouillé in 507 AD.

The sons of Clovis I, the first King of the Franks, conquered the Burgundian and the Alamanni Kingdoms. They acquired Provence, and went on to make the peoples of the Bavarii and Thuringii their clients. The Merovingians were later replaced by the new Carolingian dynasty in the 8th century. By the late 10th century, the Carolingians themselves had been replaced throughout much of their realm by other dynasties.

The Duchy of Amalfi (Latin: Ducatus Amalphitanus) or the Republic of Amalfi was a de facto independent state centered on the Southern Italian city of Amalfi during the 10th and 11th centuries. The city and its territory were originally part of the larger Duchy of Naples, governed by a patrician, but it extracted itself from Byzantine vassalage and first elected a duke (or doge) in 958.

During the 10th and 11th centuries Amalfi was estimated to have a population of 50,000–70,000 people. It rose to become an economic powerhouse, a commercial center whose merchants dominated Mediterranean and Italian trade in the ninth and tenth centuries, before being surpassed and superseded by the other maritime republics of the North and the Centre: Pisa, Venice, Genoa, Ancona and Gaeta. In 1073, Amalfi lost its independence, falling to Norman invasion and subsequently to Pisa in 1137.

The Duchy of Naples (Latin: Ducatus Neapolitanus, Neapolitan: Ducato di Napule) began as a Byzantine province that was constituted in the seventh century, in the lands roughly corresponding to the current province of Naples that the Lombards had not conquered during their invasion of Italy in the sixth century.

It was governed by a military commander (dux), and rapidly became a de facto independent state, lasting more than five centuries during the Early and High Middle Ages. Naples remains a significant metropolitan city in present-day Italy.

Duce (/ˈduːtʃeɪ/ DOO-chay, Italian: [ˈduːtʃe]) is an Italian title, derived from the Latin word dux, 'leader', and a cognate of duke. National Fascist Party leader Benito Mussolini was identified by Fascists as Il Duce ('The Leader') of the movement since the birth of the Fasci Italiani di Combattimento in 1919. In 1925 it became a reference to the dictatorial position of Sua Eccellenza Benito Mussolini, Capo del Governo, Duce del Fascismo e Fondatore dell'Impero ('His Excellency Benito Mussolini, Head of Government, Leader of Fascism and Founder of the Empire'). Mussolini held this title together with that of President of the Council of Ministers: this was the constitutional position which entitled him to rule Italy on behalf of the king of Italy. Founder of the Empire was added for the exclusive use by Mussolini in recognition of his founding of an official legal entity of the Italian Empire on behalf of the king in 1936 following Italy's victory in the Second Italo-Ethiopian War. The position was held by Mussolini until 1943, when he was removed from office by the king and the position of Duce was discontinued, while Marshal Pietro Badoglio was appointed Presidente del Consiglio.

This position was the model which other fascist leaders adopted, such as the position of Führer by Adolf Hitler and Caudillo by Francisco Franco. In September 1943, Mussolini styled himself as the "Duce of the Italian Social Republic" (Italian: Duce della Repubblica Sociale Italiana), and held the position until the collapse of the Italian Social Republic and his execution in April 1945.

Duke is a male title either of a monarch ruling over a duchy, or of a member of royalty, or nobility. As rulers, dukes are ranked below emperors, kings, grand princes, grand dukes, and above sovereign princes. As royalty or nobility, they are ranked below grand dukes and above or below princes, depending on the country or specific title. The title comes from French duc, itself from the Latin dux, 'leader', a term used in republican Rome to refer to a military commander without an official rank (particularly one of Germanic or Celtic origin), and later coming to mean the leading military commander of a province. In most countries, the word duchess is the female equivalent.

Following the reforms of the emperor Diocletian (which separated the civilian and military administrations of the Roman provinces), a dux became the military commander in each province. The title dux, Hellenised to doux, survived in the Eastern Roman Empire where it continued in several contexts, signifying a rank equivalent to a captain or general. Later on, in the 11th century, the title Megas Doux was introduced for the post of commander-in-chief of the entire navy.

Richard I (28 August 932 – 20 November 996), also known as Richard the Fearless (French: Richard Sans-Peur; Old Norse: Jarl Rikard), was the count of Rouen from 942 to 996. Dudo of Saint-Quentin, whom Richard commissioned to write the "De moribus et actis primorum Normanniae ducum" (Latin, "On the Customs and Deeds of the First Dukes of Normandy"), called him a dux. However, this use of the word may have been in the context of Richard's renowned leadership in war, and not as a reference to a title of nobility. Richard either introduced feudalism into Normandy or he greatly expanded it. By the end of his reign, the most important Norman landholders held their lands in feudal tenure.

The Principality of Dukagjini (Albanian: Principata e Dukagjinit) refers to the domains (zotërimet) of the Albanian Dukagjini family in northern Albania and western part of the modern-day territory of Kosovo in the 14th century and 15th century. At their maximum extent, the domains of the Dukagjini extended from Upper Zadrima in the northwest to the Plain of Dukagjini in western Kosovo. The political center of the Dukagjini family was Lezhë until 1393 when it was surrendered to Venice in order to not fall under the Ottomans. The Ottoman sanjak of Dukagjin was named after the rule of the family in the areas that formed it.

The Dukagjini family appears for the first time in historical record in 1281, when their progenitor Gjin Tanushi took the title of dux. They may have been descendants of the earlier Progoni family which roughly claimed the same territory as they.The Dukagjini formed their independent domains when they rebelled against the Balšić noble family. This event must have happened by 1387, because that year the brothers Pal and Lekë Dukagjini signed a trade agreement with the Republic of Ragusa and allowed free passage to the republic's merchants through their territories. It was later ruled by Pal's descendants, Tanush Dukagjini, and Pal Dukagjini II. In June 1393, the two Dukagjini brothers ceded it to Venice, which it kept until 1478 - despite later attempts by the family to retake the city. The difficult to access mountainous hinterland in the east remained under the control of the Dukagjini. In 1398, Little Tanush (son of Pal I), surrendered to the Ottomans, but in 1402, after their defeat at Ankara and the capture of Sultan Bayezid I, he freed himself from them.

Odoacer's deposition of Romulus Augustus, occurring in 476 AD, was a coup that marked the end of the reign of the last Western Roman Emperor approved by the Western Roman Senate and the creation of the Kingdom of Italy through Odoacer's decision to adopt the title of Dux/Rex Italiae(Duke/King of Italy), although Julius Nepos exercised control over Dalmatia until 480.

The Battle of Soissons was fought in 486 between Frankish forces under Clovis I and the Gallo-Roman domain of Soissons under Syagrius. The battle was a victory for the Franks, and led to the conquest of the Roman rump state of Soissons, a milestone for the Franks in their attempt to establish themselves as a major regional power.

In the final collapse of the Western Roman Empire between 476 and 480, Syagrius was the only remaining representative of Roman rule in the area between the Loire and the Somme. Syagrius was the son of Aegidius, Roman magister militum per Gallias from 457 to 461; he preserved his father's rump state, the Domain of Soissons, between the Somme and the Loire, calling himself dux.

This is a list of Roman army units and bureaucrats.

• Accensus – Light infantry men in the armies of the early Roman Republic, made up of the poorest men of the army.
• Actuarius – A soldier charged with distributing pay and provisions.
• Adiutor – A camp or headquarters adjutant or assistant.
• Aeneator – Military musician such as a bugler
• Agrimensor – A surveyor (a type of immunes).
• Antesignano – Supposedly a light infantry unit of legionaries who were used for protection of marching columns and to provide security to legions.
• Aquilifer – Bearer of the legionary eagle.
• Ala – a military formation composed of conscripts from the Italian military allies.
• Alaris – A cavalryman serving in an ala.
• Auxilia – were introduced as non-citizen troops attached to the citizen legions by Augustus after his reorganisation of the Imperial Roman army from 30 BC.
• Architecti – An engineer or artillery constructor.
• Armicustos – A soldier tasked with the administration and supply of weapons and equipment. A quartermaster.
• Ballistarius – An artillery operator (a type of immunes).
• Beneficiarius – A soldier performing an extraordinary task such as military policing or a special assignment.
• Bucellarii – were formations of escort troops.
• Bucinator – A trumpeter or bugler.
• Cacula – Servant or slave of a soldier.
• Capsarior – A medical orderly.
• Causarius – A soldier discharged for wounds or other medical reasons.
• Celeres - A royal guard created by Romulus to guard the King of Rome.
• Centurion – Officer rank, generally one per 80 soldiers, in charge of a centuria.
• Clinicus – A medic.
• Cohors amicorum – Military staff company functioning as suite and bodyguard of a high Roman official.
• Comes – commanders of comitatenses. The authority of a comes was limited to his assigned territory. This title later evolved to the medieval title of Count.
• Comes stabuli – An office responsible for the horses and pack animals.
• Comitatenses – units of the field armies of the late empire. They were the soldiers that replaced the legionaries.
• Cornicen – A bugler.
• Doctor – A trainer, subdivisions for everything from weapons to horn blowing.
• Draconarius – Bearer of a cavalry standard.
• Decurion – Leader of a troop of cavalry (14-30 men). Not to be confused with decanus.
• Decanus – Leader of a contubernium (a legionary tent group of 8 men). Elected by the members of the contubernium.
• Discens – Miles (enlisted soldier) in training for an immunis position.
• Duplarius – A soldier issued double pay, such as an Optio or a minor cavalry officer as part of a Turma
• Dux – A general in charge of two or more legions. In the Third Century AD, an officer with a regional command transcending provincial boundaries, responsible directly to the emperor alone, usually appointed on a temporary basis in a grave emergency. In the fourth century AD, an officer in charge of a section of the frontier answering to the Magister Militum. Later developed into the medieval title Duke.
• Duumviri navales – Two men elected to equip and repair the Roman navy.
• Equites singulares Augusti – Elite cavalry unit tasked to guard the Roman Emperors. Usually commanded by a tribunus of praetorian rank.
• Evocatus – "One who is called back." A soldier who had served out his time and obtained his discharge (missio), but had voluntarily enlisted again at the invitation of the consul or other commander.
• Evocatus Augusti – Praetorian Guard who had served out his time and obtained his discharge (missio), but had voluntarily enlisted again.
• Equites – Roman cavalry. Those citizens whose personal wealth was sufficient to own and equip a horse for cavalry, later evolved into a socioeconomic distinction unrelated to military service.
• Foederati – For groups of "barbarian" mercenaries of various sizes who were typically allowed to settle within the empire after service in the imperial army. Foederati, unlike auxilia which were commanded by Roman officers, and enlisted under the promise of obtaining Roman citizenship after completing their term of service of 20 to 25 years, were enlisted as an entire tribal unit, serving under native commanders, and not eligible to receive citizenship. Originally paid in money, but as the finances of the Late Empire declined, service in exchange for land became the norm. The sack of Rome in the 5th century by Vandals and Ostrogoths were precipitated by the Senate's failure to pay foederati as promised after their military service. The system of land tenure established by the settlement of foederati, whose leaders were granted territories as their personal property, developed into the medieval system of feudalism.
• Frumentarii – Officials of the Roman Empire during the 2nd and 3rd era. Often used as a Secret Service, mostly operating in uniform.
• Hastatus – The youngest of the heavy infantry in the pre-Marian armies, who were less well-equipped than the older Principes and Triarii. These formed the first line of battle in front of the Principes.
• Hastatus Prior – A centurion commanding a manipulus or centuria of hastati. A high-ranking officer within a manipulus or centuria.
• Hastatus Posterior – A deputy to the hastatus prior
• Hastiliarius – A weapons instructor.
• Imaginifer – A standard-bearer carrying the imago – the standard which bore a likeness of the emperor, and, at later dates, his family.
• Immunes – Soldiers who were "immune" from combat duty and fatigues through having a more specialist role within the army.
• Jovians and Herculians – A senior palatine units
• Katepano – A Byzantine military rank or military official.
• Laeti – was a term used in the late empire to denote communities of foreigners permitted to settle on, and granted land in, imperial territory on condition that they provide recruits for the Roman military.
• Legatus legionis – A legion commander of senatorial rank; literally the "deputy" of the emperor, who was the titular commander-in-chief.
• Limitanei – A unit of frontier districts.
• Legatus pro praetore – Provincial governor of senatorial rank with multiple legions under his command.
• Legionary – The heavy infantry that was the basic military force of the ancient Roman army in the period of the late Roman Republic and the early Roman Empire.
• Magister militum - High ranked commander in the late Roman Empire. Equivalent of a general.
• Medicus – Physician or combat medic. Specializations included surgery (medicus vulnerarius), ophthalmology (medicus ocularius), and also veterinary (medicus veterinarius). At least some held rank equivalent to a centurion.
• Megas doux – Commander-in-chief of the Byzantine navy.
• Miles or Miles Gregarius – The basic private level foot soldier.
• Numerus – A unit of foreign allies not integrated into the regular army structure. Later, a unit of border forces.
• Numerus Batavorum – was a personal, imperial guards unit for the Roman emperors of the Julio-Claudian dynasty (30 BC – AD 68) composed of Germanic soldiers.
• Optio – One per century as second-in-command to the centurion. Could also fill several other specialized roles on an ad hoc basis.
• Palatini – were elite units of the late army.
• Pedites – The infantry of the early army of the Roman kingdom. The majority of the army in this period.
• Peditatus – A term referring to any infantryman in the Roman Empire.
• Pilus Prior – Senior centurion of a cohort.
• Pilus Posterior – Deputy to the pilus prior.
• Praefectus Castrorum – Camp prefect, third-in-command of the legion, also responsible for maintaining the camp, equipment, and supplies. Usually a former primus pilus.
• Praefectus Cohortis - Commander of a cohort.
• Praefectus legionis agens vice legati – Equestrian officer given the command of a legion in the absence of a senatorial legatus. After the removal of senators from military command, the title of a legionary commander. ("...agens vice legati, dropped in later Third Century")
• Praetorians – A special force of bodyguards used by Roman Emperors.
• Praetorian prefect – Commander of the Praetorians.
• Primani – was a legio palatina, active in the 4th and 5th century.
• Primicerius – was a rank junior to the tribunus and senior to the senator.
• Primus Ordinis – The commanding officer of each centuria in the first cohort with the exception of the first centuria of the cohort.
• Primus Pilus (literally 'first file' ) – The centurion commanding the first cohort and the senior centurion of the entire Legion.
• Princeps – Pre-Marian soldier, initially equipped with the Hasta spear, but later with the pilum, these men formed the second line of battle behind the Hastati in the pre-Marian armies. They were also chieftains in Briton like Dumnorix of the Regneses (he was killed by Gaius Salvius Liberalis' soldiers).
• Princeps Prior – A centurion commanding a century of principes.
• Princeps Posterior – A deputy to the princeps prior.
• Principales – A group of ranks, including aquilifer, signifer, optio, and tesserarius. Similar to modern NCOs (Non-commissioned officers).
• Protectores Augusti Nostri (a.k.a. Protectores Divini Lateris) – Honorific title for senior officers singled out for their loyalty to the Emperor and soldierly qualities. The protectores were an order of honor rather than a military unit. The order first appeared in the mid-200s AD.
• Quaestionarius – An interrogator or torturer.
• Retentus – A soldier kept in service after serving required term.
• Rorarii – The final line, or reserve, in the ancient pre-Marius Roman army. These were removed even before the so-called "Marian reforms", as the Triarii provided a very sturdy anchor.
• Sagittarii – Archers, including horse-riding auxiliary archers recruited mainly in North Africa, Balkans, and later the Eastern Empire.
• Salararius – A soldier enjoying special service conditions or hired as a mercenary.
• Scholae – was used in the late Roman Empire to signify a unit of Imperial Guards.
• Scholae Palatinae – An elite troop of soldiers created by the Emperor Constantine the Great to provide personal protection of the Emperor and his immediate family.
• Scorpionarius – An artilleryman operating a scorpio artillery piece.
• Sesquiplicarii – A soldier issued one-and-a-half times pay, such as a Tesserarius or a minor cavalry officer as part of a Turma
• Signifer – Standard bearer of the Roman Legion.
• Simplares - A soldier paid standard pay; a regular legionaire or somebody paid the equivalent
• Socii – Troops from allied states in the pre-Marian army before the Social War (91–88 BC)
• Speculatores and Exploratores – The scouts and reconnaissance element of the Roman army.
• Supernumerarii – Supernumerary soldiers who served to fill the places of those who were killed or disabled by their wounds. Also used for the cavalry contingent of a legion during the Principate, who despite being included on the cohort lists, camped separate to the infantry.
• Strategos - General and military governor of a theme in the Byzantine Empire.
• Stratelates – A Greek translation for the rank of magister militum that was used in the late Roman and Byzantine armies.
• Stratopedarches – A term originally used to refer to a Roman camp prefect, it was later used for a Roman or Byzantine general or a Byzantine commander-in-chief.
• Tablifer – A standard-bearer for the guard cavalry.
• Tesserarius – Guard commander, one per centuria.
• Tirones – A basic trainee.
• Torquati - A soldier issued with a golden collar in reward for bravery or valor. Depending on circumstances, they may also be rewarded with double pay, making them Torquato Duplares
• Triarii – Spearmen of the pre-Marian armies, equipped with the Hasta, who formed the third line of battle behind the Principes.
• Tribuni angusticlavii – Military tribune of equestrian rank, five of whom were assigned to each legion.
• Tribunus militum - Officer in the Roman army who ranked below the legate but above the centurion.
• Tribunus militum laticlavius – Military tribune of senatorial rank. Second in command of a legion. Appointments to this rank seem to have ceased during the sole reign of Gallienus as part of a policy of excluding senators from military commands.
• Tubicen – A trumpeter.
• Urbanae – A special police force of Rome, created to counterbalance the Praetorians.
• Velites – A class of light infantry in the army of the Roman Republic.
• Venator – A hunter (a type of immunes).
• Vexillarius – Bearer of a vexillum (standard).
• Vigiles – were the firefighters and police.