From its origin as a city-state on the peninsula of Italy in the 8th century BC, to its rise as an empire covering much of Southern Europe, Western Europe, Near East and North Africa to its fall in the 5th century AD, the political history of Ancient Rome was closely entwined with its military history. The core of the campaign history of the Roman military is an aggregate of different accounts of the Roman military's land battles, from its initial defense against and subsequent conquest of the city's hilltop neighbors on the Italian peninsula, to the ultimate struggle of the Western Roman Empire for its existence against invading Huns, Vandals and Germanic tribes. These accounts were written by various authors throughout and after the history of the Empire. Following the First Punic War, naval battles were less significant than land battles to the military history of Rome due to its encompassment of lands of the periphery and its unchallenged dominance of the Mediterranean Sea.
The Roman army battled first against its tribal neighbours and Etruscan towns within Italy, and later came to dominate the Mediterranean and at its height the provinces of Britannia and Asia Minor. As with most ancient civilizations, Rome's military served the triple purpose of securing its borders, exploiting peripheral areas through measures such as imposing tribute on conquered peoples, and maintaining internal order. From the outset, Rome's military typified this pattern, and the majority of Rome's campaigns were characterised by one of two types. The first is the territorial expansionist campaign, normally begun as a counter-offensive, in which each victory brought subjugation of large areas of territory and allowed Rome to grow from a small town to a population of 55 million in the early empire when expansion was halted. The second is the civil war, which plagued Rome from its foundation to its eventual demise.