The Military of ancient Rome relates to the combined military forces of Ancient Rome from the founding of the city of Rome in the 8th century BC to the fall of the Western Roman Empire in the 5th century AD. Originally The Roman military consisted entirely of the Roman army, but a small navy was first added during the Samnite Wars and later significantly expanded. The Roman military was intertwined with the Roman state much more closely than in a modern Western nation. Josephus describes the Roman people as "as if born ready armed." and the Romans were for long periods prepared to engage in almost continuous warfare.
For a large part of Rome's history, the Roman state existed as an entity almost solely to support and finance the Roman military. The military's campaign history stretched over 1300 years and saw Roman armies campaigning as far East as Parthia, as far south as Africa and as far north as Britannia.
The makeup of the Roman military changed substantially over its history, from its early history as an unsalaried citizen militia to a later professional force. The equipment used by the military altered greatly in type over time with the Romans adapting to circumstance and showing a willingness to utilise the technology of their enemies, though there were very few technological improvements in weapons manufacture, like the rest of the classical world. For much of its history, the majority of Rome's forces were maintained at or beyond the limits of its territory, in order to either expand Rome's domain, or protect its existing borders.
The structural history of the Roman military describes the major chronological transformations in the organization and constitution of ancient Rome's armed forces, "the most effective and long-lived military institution known to history". From its origins around 800 BC to its final dissolution in 476 AD with the demise of the Western Roman Empire, Rome's military underwent substantial structural change. At the highest level of structure, Rome's forces were split into the Roman army and the Roman navy, although these two branches were less distinct than in a modern national defence force. Within the top-level branches of army and navy, structural changes occurred both as a result of positive military reform and through organic structural evolution.The earliest Roman army mentioned in writing is ascribed by our much later sources, Livy and Dionysius of Halicarnassus, to the 8th century BC; and is often referred to as Rome's curiate army, named for the subdivisions of the army based upon the three founding tribes (Latin: curiae) of Rome. This army was a relatively small force, and its activities were limited "mainly [to] raiding and cattle rustling with the occasional skirmish-like battle".
Marcus Ulpius Nerva Traianus, commonly called Trajan, lived from September 18, 53 to August 9, 117. He was a Roman Emperor from 98–117. He was the second of the "Five Good Emperors of the Roman Empire". From 101-102, and then from 105-106 he launched the Dacian Wars, ending with Dacia being added to the Roman Empire as yet another province. From 113-116, he led the successful invasions of Armenia, Persia, and Mesopotamia, bringing the Empire to its greatest territorial extent. He died soon after the invasions in 117, and his adopted son Hadrian took the throne. Soon after Hadrian took the throne, he lost most of the eastern territory, yet Dacia remained a Roman province.
Roman, remember that you shall rule the nations by your authority, for this is to be your skill, to make peace the custom, to spare the conquered, and to wage war until the haughty are brought low., Virgil, Aeneid
Alea iacta est (The die is cast), reportedly said by Gaius Julius Caesar before crossing the Rubicon
Silent enim leges inter arma (Laws are silent in times of war), Cicero
War gives the right of the conquerors to impose any conditions they please upon the vanquished. , Gaius Julius Caesar
The outcome corresponds less to expectations in war than in any other case whatsoever, Livy
A bad peace is even worse than war. , Tacitus
Veni, Vidi, Vici (I came, I saw, I conquered), Gaius Julius Caesar
I found Rome brick, I left it marble., Caesar Augustus