same time, the dilapidated fortifications were also upgraded at Edessa, Batnae and Amida. Although no further large-scale conflict took place during Anastasius' reign, tensions continued, especially while work proceeded at Dara. This was because the construction of new fortifications in the border zone by either empire had been prohibited by a treaty concluded some decades earlier. Anastasius pursued the project despite Persian objections, and the walls were completed by 507–508. . The siege of the city proved to be a far more difficult enterprise than Kavadh expected; the defenders repelled the Persian assaults for three months before being defeated. In 503 the Romans attempted an ultimately unsuccessful siege of the Persian-held Amida while Kavadh invaded Osroene, and laid siege to Edessa with the same results. Finally in 504, the Romans gained the upper hand with the renewed investment of Amida, leading to the hand-over of the city. That year an armistice was agreed to as a result of an invasion of Armenia by the Huns from the Caucasus. Negotiations between the two powers took place, but such was their distrust that in 506 the Romans, suspecting treachery, seized the Persian officials. Once released, the Persians preferred to stay in Nisibis. In November 506, a treaty was finally agreed upon, but little is known of what the terms of the treaty were. Procopius states that peace was agreed for seven years, and it is likely that some payments were made to the Persians. In 505 Anastasius ordered the building of a great fortified city at Dara. The dilapidated fortifications were also upgraded at Edessa, Batnac and Amida. Although no further large-scale conflict took place during Anastasius' reign, tensions continued, especially while work continued at Dara. This construction project was to become a key component of the Roman defenses, and also a lasting source of controversy with the Persians, who complained that it violated the treaty of 422, by which both empires had agreed not to establish new fortifications in the frontier zone. Anastasius, however, pursued the project, and the walls were completed by 507/508. Iberian War In 524–525 AD, Kavadh proposed that Justin I adopt his son, Khosrau, but the negotiations soon broke down. The proposal was initially greeted with enthusiasm by the Roman emperor and his nephew, Justinian, but Justin's quaestor, Proculus, opposed the move. Tensions between the two powers were further heightened by the defection of the Iberian king