Battle of Sarmisegetusa The Battle of Sarmizegetusa ( also spelled " Sarmizegethusa " ) was a siege of Sarmizegetusa , the capital of Dacia , fought in 106 between the army of the Roman Emperor Trajan , and the Dacians led by King Decebalus . Background . Due to the threat the Dacians represented to the Roman Empire ' s eastward expansion , in the year 101 Emperor Trajan made the decision to begin a campaign against them . The first conflict began on March 25 and the Roman troops , consisting of four principal legions , the units X " Gemina " , XI " Claudia " , II " Traiana Fortis " and XXX " Ulpia Victrix " , defeated the Dacians , and it thus ended in Roman victory . Although the Dacians had sustained a defeat during the First Dacian War , the emperor postponed the final assault on their capital of Sarmizegetusa to reorganize his troops . Trajan demanded severe concessions from the Dacians and very hard peace conditions : Decebalus had to renounce all claims to portions of his kingdom , including Banat , Tara Haţegului , Oltenia , and Muntenia in the region south - west of Transylvania . He also had to surrender all Roman deserters his troops had captured as well as the Dacian war machine s . Upon returning to Rome , Trajan was welcomed as victorious leader , and in honor of his triumph he took the name of " Dacicus " , a title that appears on his coinage of this period . However , during the years 103 – 105 , Decebalus did not respect the peace conditions imposed by Trajan , and in retaliation the Emperor prepared to annihilate the Dacian kingdom and finally conquer Sarmizegetuza . The siege of Sarmizegetuza took place in the summer of the year 106 . It is estimated that the Dacians most likely had less than 20 , 000 men capable of fighting the invasion . Advance . The Roman forces approached Sarmizegetuza in three main columns . The first column crossed the bridge built by Apollodorus of Damascus , and then followed the valleys of rivers Cerna and Timiş up to Tibiscum . They then turned on the valley of the river Bistra , through the Tara Haţegului depression . In these places , there were already Roman garrisons stationed from the first war , greatly easing the advance . They passed through Valea Cernei , Haţeg , and Valea Streiului and destroyed the Dacian fortresses at Costesti , Blidaru , and Piatra Rosie . The second column of the army is believed to have crossed the Danube somewhere near ancient Sucidava and then marched northwards on the valley of Jiu , linking with the first Roman column in Tara Haţegului . The combined forces of the two columns then began attacking the area of the Şurianu Mountains , meeting sporadic but desperate resistance from the Dacians . The third Roman column , most likely led by Trajan himself , advanced through eastern Muntenia , crossed the Carpathians at a location close to what is now Bran , and marched westwards through southern Transylvania . The rest of the troops left from Moesia Inferior and passed through Bran , Bratocea , and Oituz and destroyed the Dacian fortresses between Cumidava ( now Rasnov , in Romania ) and Angustia ( now Brețcu , in Romania ) . At the battle for the conquest of Sarmizegetuza the following legions participated : II " Adiutirx " , IV " Flavia Felix " , and a " vexillatio " of VI " Ferrata " which until this war had been stationed in Iudaea . The Roman forces then enveloped Sarmizegetuza . Other Roman units are believed to have attacked other Dacian settlements and rally points , as far as the river Tisa to the north , and Moldavia to the east . Dacian settlements in the west , such as Ziridava , were completely destroyed in this period . However , Moldavia and Maramureş , located in modern day northern Romania , were never part of the Roman province of Dacia and would remain free from Roman rule . Siege . The only historical record of the siege is the Trajan ' s Column , which is a controversial source . There is debate as to whether the Romans did actually fight for Sarmizegetuza , or whether the Dacians destroyed their capital while fleeing ahead of the advancing legions . Most historians agree that a siege of Sarmizegetuza actually took place . The first assault was repelled by the Dacian defenders . The Romans bombarded the city with their siege weapons and , at the same time , they built a platform to more easily breach the fortress . They also encircled the city with a " circumvallatio " wall . Finally , the Romans destroyed the water pipes of Sarmizegetuza and obliged the defenders to surrender before they set fire to the city . Roman forces succeeded in entering the Dacian sacred enclosure , hailed Trajan as emperor , and then leveled the whole fortress . IV " Flavia Felix " was stationed there to guard the ruins of Sarmizegetuza . Following the conclusion of the siege , Bicilis , a confidant of Decebalus , betrayed his king , and led the Romans to the Dacian treasure which , according to Jerome Carcopino ( p . 73 ) , consisted of 165 , 000 kilograms of pure gold and 331 , 000 kilograms of silver in the bed of the Sergetia River ( Cassius Dio 68 . 14 ) . Aftermath . Decebalus and many of his followers escaped the Legions during the siege . They fled east , probably towards the fortification of Ranisstorum , the location of which is now lost , only to be caught by the Roman cavalry . Knowing the often brutal treatment of prisoners of war taken by the Romans , Decebalus killed himself to avoid capture . Decebalus ' head and right arm were later presented to Trajan . The Romans reorganized Dacia as a Roman province and built another capital - city at a distance of 40 kilometers from the old Sarmizegetuza . This center was named " Colonia Ulpia Traiana Dacica Augusta Sarmizegetuza " . The Roman Senate celebrated the founding by ordering the minting of a sestertius dedicated to the " optimus princeps " . Losses sustained in this war by the Dacians were tremendous , but the Roman army also took significant casualties in the conquest of Dacia . The first Dacian rebellion against Roman rule would coincide with the death of Trajan , in 117 , showing impact the Emperor had on the Dacians after the war . Even in modern Romanian folklore , Trajan was remembered as Traian , and his great wars with the " people of the mountains " are still remembered in Romanian epic songs . Whilst the battle ended in Roman victory , it is considered by historians as the last great conquest of the Roman Empire before its eventual decline .