Some writers, doubtless bearing in mind the hardihood and bravery of the native inhabitants and the mountainous and thus easily defended nature of the ground the Roman legions had to traverse and fight over, have expressed some surprise at the comparative ease with which Drusus and Tiberius appear to have accomplished the conquest of the country. More perfect discipline and arms of greater effectiveness will not, however, we think, altogether account for this, for history has over and over again proved that knowledge of the ground by the defenders and mountainous regions count heavily against successful attacks on the part of an invader. It can only therefore be supposed that the various tribes who formed the inhabitants of Rhætia were either antagonistic to one another or at least were not welded together in a common cause against the invading Roman hosts, and thus the country was conquered and kept in subjection with greater ease than would otherwise have been the case. As a result of the invasion by Drusus and Tiberius and the Roman legions the tract of country then and for some considerable time afterwards known as Rhætia, but now known as Tyrol and the Vorarlberg, ultimately became Romanized, and by the making of the Brenner Post Road, which was constructed by the direction of the Emperor Augustus between Verona and Augsburg (Augusta Vindelicorum), communication between the Germanic Empire and Italy was opened up. Thus was the lowest and most accessible of the passes over the mountains which separated Italy from the barbaric regions beyond crossed by one of those splendid military roads, which has endured nearly two thousand years until the present day. [Sidenote: ROMAN OCCUPATION] The Roman occupation of Rhætia lasted for five centuries. Under the rule of Rome the inhabitants learned much of those arts which remained the heritage of conquered races long after the sway of the great Roman Empire had come to an end. And traces of that rule, in the form of weapons, ornaments, articles of jewelry and the toilet, and other relics have from time to time come to light throughout the portions of Tyrol settled by the Romans.