The intellectual and spiritual life of the partly Hellenized and, at last, Christianized, Roman Empire furnished the contents of the intellectual and spiritual development of the Middle Ages.[17] In Latin forms the Christian and antique elements passed to the mediaeval period. Their Latinization, their continuance, and their passing on, were due to the existence of the Empire as a political and social fact. Rome’s equal government facilitated the transmission of Greek thought through the Mediterranean west; Roman arms, Roman qualities conquered Spain and Gaul, subdued them to the Roman order, opened them to Graeco-Latin influences, also to Christianity. Indelibly Latinized in language and temper, Spain, Gaul, and Italy present first a homogeneity of culture and civic order, and then a common decadence and confusion. But decadence and confusion did not obliterate the ancient elements; which painfully endured, passing down disfigured and bedimmed, to form the basis of mediaeval culture. The all-important Latinization of western Europe began with the unification of Italy under Rome. This took five centuries of war. In central Italy, Marsians, Samnites, Umbrians, Etruscans, were slowly conquered; and in the south Rome stood forth at last triumphant after the war against Tarentum and Pyrrhus of Epirus. With Rome’s political domination, the Latin language also won its way to supremacy throughout the peninsula, being drastically forced, along with Roman civic institutions, upon Tarentum and the other Greek communities of Magna Graecia.[18] Yet in revenge, from this time on, Greek medicine and manners, mythology, art, poetry, philosophy--Greek thought in every guise--entered the Latin pale. At the time of which we speak, the third century before Christ, the northern boundaries of Italy were still the rivers Arno and, to the east, the Aesis, which flows into the Adriatic, near Ancona. North-west of the Arno, Ligurian highlanders held the mountain lands as far as Nice. North of the Aesis lay the valley of the Po. That great plain may have been occupied at an early time by Etruscan communities scattered through a Celtic population gradually settling to an agricultural life. Whatever may be the facts as to the existence of these earlier Celts, other and ruder Celtic tribes swarmed down from the Alps[19] about 400 B.C., spread through the Po Valley, pushing the Etruscans back into Etruria, and following them there to carry on the war. After this comes the well-known story of Roman interference, leading to Roman overthrow at the river Allia in 390, and the capture of the city by these “Gauls.” The latter then retired northward, to occupy the Po Valley; though bands of them settled as far south as the Aesis.