218 BC The Romans arrive in the Iberian peninsula
Their initial motive is to dislodge the Carthaginians, who had an expanding military presence on the south and east coasts at the time of Hannibal in the second Punic war. Defeating the Carthaginians in Iberia was to take the Romans 12 years.
The Romans then set about colonising the whole peninsula, both Spain and modern Portugal. This was to take 200 years to complete, and involved the Republic's two top generals, Julius Caesar and Pompey the Great, at various stages. It was a considerable undertaking, involving at its maximum seven Roman legions in the field at the same time.
The Romans bring Latin. Modern Portuguese is basically still Latin - optimised over the years for poetry and song.
Ângela Silva Rodrigo Leão "Carpe diem"
Ângela Silva sings composer Rodrigo Leão's "Carpe diem" (Seize the day) in Latin
This is a hymn to love made up of common Latin phrases. Though Latin is not widely understood now, Portuguese singers don't have much trouble with the pronunciation and phrasing.
139 BC Death of Viriatus - resistance begins to fade
Viriatus (Viriato in Portuguese) is the Portuguese equivalent of Vercingetorix in France and Boudica or Caratacus in Britain. Resistance to the Romans was most intense in the upper Douro valley, on both the Portuguese and Spanish sides of the modern border.
Local hero Viriatus, hailing from somewhere in the Douro valley, is celebrated today in both countries. After numerous victories Viriatus was finally killed by treachery (like that other famous enemy of Rome, Arminius in Germany).