'Commotions about the same time broke out amongst the Dacians, a people never to be relied on, and since the legions were withdrawn from Mœsia there was no force to awe them. They, however, watched in silence the first movements of affairs. But when they heard that Italy was in a blaze of war, and that all the inhabitants were in arms against each other, they stormed the winter quarters of the cohorts and the cavalry, and made themselves masters of both banks of the Danube. They then prepared to raze the camp of the legions, when Mucianus sent the sixth legion to check them, having heard of the victory at Cremona, and lest a formidable foreign force should invade Italy on both sides, the Dacians and the Germans making irruptions in opposite quarters. On this, as on many other occasions, fortune favoured the Romans in bringing Mucianus and the forces of the East into that quarter, and also in that we had settled matters at Cremona in the very nick of time.'[81]

It was in the reign of the Emperor Domitian, however, that the inroads of the Dacians assumed their most formidable proportions. About this time it is probable that the Dacians were divided into several tribes, and that one leader more powerful than the rest had secured the chieftainship of the whole nation. Thia chief is known to historians as 'Decebalus,' although there is great difference of opinion as to whether that was his name or his title.[82] In the year 86 a.d., he gathered together a great host, and, crossing the Danube into Mœsia, defeated and killed the prætor Oppius or Appius Sabinus, seizing several of the Roman fortresses and driving their army to the foot of Mount Hæmus. As soon as the defeat and the position of the Roman forces became known, Domitian collected an army in Illyria and placed it under the command of Cornelius Fuscus, a general of more bravery than experience, who entered Mœsia, and, finding that Decebalus, according to precedent, had retired across the Danube, followed him into his own country, only, however, in his turn to be defeated and slain. Upon this the Romans again recrossed the river, leaving behind them their baggage and many prisoners. Tacitus writes in great indignation concerning these reverses:—

'So many armies in Mœsia, Dacia, Germany, and Pannonia, lost through the temerity or cowardice of their generals; so many men of military character with numerous cohorts defeated and taken prisoners; whilst a dubious contest was maintained, not for the boundaries of the Empire and the banks of the bordering rivers, but for the winter quarters of the legions and the possession of our territories.'[83]

Whilst these events were occurring, Domitian is said to have been making progresses and indulging in all kinds of excesses, but; fortunately for him and for the honour of the Roman arms, another general succeeded in stemming the tide of invasion, and eventually (a.d. 89) in assuming the offensive. This was Tertius Julianus, who had already distinguished himself in Mœsia under Otho and Vespasian. Following Decebalus into his own dominions, he was not content to remain in the plains, but pursued him into his mountain retreats, where he completely overthrew him in a pitched battle and compelled him to sue for peace. It is in the accounts of this expedition that mention is first made of regular roads in Dacia, and two passes, the Vulcan and Rothenthurm (or Red Tower), are referred to. A place called Tapæ is also named, near to which Julianus is said to have overthrown Decebalus, and where subsequently Trajan obtained a victory over the same prince; but so much doubt attaches to the movements of Julianus that it will be better for the present to defer any reference to those localities. The whole account of Julianus's campaign in Dacia is mixed up with legendary tradition. It is said that he threatened the capital of Dacia, Sarmizegethusa, and that he would have succeeded in capturing it and in reducing the whole country but for a stratagem of Decebalus, who caused trees to be cut down to a man's height in the woods through which the Romans had to pass, and clothed them in armour, which so terrified the soldiers as to stay their progress. According to another account he cut the trees through their trunks but allowed them to stand, and when the Romans attempted to force their way through with their engines of war, the trees fell on them and killed them. Whether it was the difficulty encountered by the Roman general in attempting to cope with his warlike enemy in his mountains and forests, where the arts of war as practised by the former were not so readily applicable as in the plains, or the more probable circumstance that Domitian had been unsuccessful in an expedition against two other tribes, the Quadi and Marcomanni, and needed the support of Julianus, certain it is that the overtures of Decebalus were at length received favourably, and a peace was concluded with him in the year 90, which was less favourable to the victors than to the conquered. Decebalus refused to treat in person with the Roman general, but sent one of his chiefs (some historians say his brother), with whom the conditions were arranged. According to Roman accounts Decebalus restored the Roman prisoners, acknowledged the supremacy of Domitian, and accepted sovereignty at his hands. It subsequently transpired, however, that this was not the whole treaty, and that Domitian agreed to pay the Dacian king an annual tribute, and to send him a number of skilled artificers to teach him the art of constructing works and fabricating arms upon the Roman model. Domitian then celebrated a triumph, which was however made a subject of ridicule by those who were aware of the actual result of the expedition.

We now approach a crisis in the history of Dacia. During the short reign of Nerva nothing was undertaken against the country, and Decebalus continued to harass and annoy the Romans in Mœsia until Trajan (who had been adopted by Nerva) ascended the throne (a.d. 98).

This emperor at once began preparations for putting an end to his humiliating relations with Decebalus and his people, and although there have been many conjectures concerning his motives and intentions, there can be little doubt that his object was eventually, if not immediately, to incorporate Dacia with his empire. Already in the reign of some of his predecessors the construction of a military road along the right or south bank of the Danube had been proceeding, and the first operation of Trajan was to hasten the completion of this road for the passage of his troops.[84] With this object he is said to have reconnoitred in 98 and 99, and the road probably attained completion as far as the bank opposite Orsova, about a.d. 100, as the tablet at Gradina, to which reference has already been made, indicates. It is impossible for us to estimate the difficulties which must have attended this undertaking. Possessing as we do explosives and rock-borers with which to break a passage through mountains and to blast rocky embankments, we can hardly understand how a people, with such limited mechanical appliances as then existed, can have surmounted the obstacles that presented themselves to their progress. In one place the way was a plank road resting on beams, which were driven into the perpendicular face of the solid rock a few feet above the water's edge, whilst a little further on it is seen to wind along terraces cut artificially, high up on the hillsides. Hundreds if not thousands of lives must have been sacrificed in the work, for it must be remembered that the Roman generals and artificers had not only to combat natural difficulties, and to overcome the same obstacles as those which our modern engineers have to face, but that they were harassed by the savage but skilled enemy from the heights above, or from the opposite bank of the river, which here and there narrows itself into defiles 150 or 200 yards wide.

As soon as the road was sufficiently advanced for the passage of his army, a.d. 101, Trajan commenced his first expedition into Dacia. The constitution and number of his forces are not accurately known.[85] They varied, according to different accounts, from 60,000 to 80,000 Romans, with a considerable number of allies, Germans, Sarmatians, Mauritanian cavalry, &c., the last-named under Lucius Quietus; and these Trajan is said to have assembled at a place somewhere south of Viminacium, which subsequently served as the base of his operations.[86]

Pages upon pages have been devoted by ancient and modern historians to surmises concerning the routes taken by Trajan in his expedition and the localities where his encounters with the Dacians took place, but in every case the ascertained facts have been few in number. The best history of the campaigns is delineated in the bas-reliefs on Trajan's Column[87] at Rome, and many details have been collected from fragmentary writings of Dion Cassius and other old historians.

For the convenience of crossing the Danube the army was divided into two parts, and the river was crossed by bridges of boats at two points, one near Viminacium and the other opposite Orsova. The first section then skirted the western slopes of the Carpathians through the valley of the Theiss, and so entered the Dacian highlands; the other marched up the valley of the Tierna (Czerna), past the baths of Mehadia, which already existed in the Roman period, and the two divisions of the army formed a junction at Karansebes,[88] or at Tibiscum close by, where two Roman roads met; Trajan is known to have accompanied and led the eastern division until the junction was completed. It is probable that in that year (101 a.d.) no serious encounter took place between Trajan and Decebalus, who had been occupied for some time in preparing for his defence, and had now received reinforcements from many of the neighbouring tribes. One of these in the name of the allied tribes sent a threatening message to Trajan, written or scratched upon a fungus, warning him to withdraw his troops, but he heeded neither this admonition nor overtures of peace proceeding from Decebalus himself. His army went into winter quarters, and early in 102 a.d. he commenced operations by forcing the Iron Gate pass in the Carpathians,[89] and encountered the enemy, it is said, at the same place where Julianus had previously defeated Decebalus, namely, Tapæ.[90] Here the Dacians again met with a sanguinary defeat, but the Romans also sustained severe losses, and Trajan secured himself in the affections of his soldiers by tearing up his garments to make bandages for the wounded.[91] After this reverse Decebalus sought to reopen negotiations with Trajan, but on his refusal to receive the emissaries of the emperor, who declined to meet him in person, hostilities were renewed, and the war was prosecuted by the Dacians with great fierceness and barbarity. The discipline and warlike resources of Rome, however, maintained the ascendency for her arms. Decebalus was pressed from stronghold to stronghold, and defeated in one encounter after another, until at length his capital Sarmizegethusa was threatened by his triumphant enemy. Then it was that he sued earnestly for peace, and accepted the unfavourable conditions offered him by Trajan. He was compelled to give up all his war material and artificers, to raze his fortresses, to deliver up all Roman prisoners and deserters, to conclude a treaty defensive and offensive with Rome, and to appear before and do homage to the emperor. Dacia thus became a vassal but autonomous province of the Empire, and, content with his victory, Trajan returned to the capital, taking with him certain Dacian chiefs, who repeated the act of homage in the senate. He then celebrated a triumph, and received the distinctive title of 'Dacicus.'[92]