This complex network of ties betweenGreek- and Slavonic-speaking orthodox potentates presupposed an effective Latin threat, and had as its axis the agreement between Epiros and the Bulgarians; however, this alliance could never be more than opportunistic. Bulgaria recovered its strength under Ivan II Asen (1218–41), and Ivan made no secret of his ambition to take Constantinople, which was also the target of the Epirot ruler in his struggle against his Nicaean rival. The Bulgarians also had their eye on the Adriatic, and could not forget that their ambassadors to the pope had been unable to proceed further than Dyrrachium.49 The death of the Latin emperor Henry in 1216, and the defeat of Peter of Courtenay the following year, revitalised the three powers aiming for Constantinople: Nicaea, Epiros and Bulgaria. The latter realm under Ivan Asen enjoyed its last spell of greatness in the middle ages; from then on, its rulers were primarily concerned with undermining the Greek contenders for the throne in Constantinople, playing off the various factions. The City itself was almost within their sights by 1225, and the Latins were prompted to seek a Bulgarian alliance three years later upon the death of Emperor Robert of Courtenay (1218–28) and with the prospect of a minor, his brother Baldwin, mounting the throne. A marriage was planned between Baldwin II (1237–61) and Ivan’s daughter Helena. Ivan was attracted by the prospect of gaining the regency of the Latin empire and in April 1229 he disregarded promises made earlier to the elderly John of Brienne. However, these plans only resulted in a breach with Theodore Angelos of Epiros.50 In spring 1230, taking the view that he could not march on Constantinople without first removing the Bulgarians’ threat to his rear,51 Theodore Angelos decided to attack them. He was crushed in battle at Klokotnitsa in theMaritsa valley,52 captured and blinded; this defeat sealed the fate of the westernmost of theGreek rump states.53 In April 1230, Ivan Asen launched a sweeping counter-offensive, gaining Adrianople,Didymoteichon, Boleron, Serres, Pelagonia (Bitola) and Prilep, as well as Thessaly and Albania right up to the gates of Dyrrachium; the town itself apparently escaped his control. 54 It is not clear whether the Bulgarians achieved their ambition of ruling from coast to coast, from the Adriatic to the Aegean. An agreement between Ivan and Dubrovnik of 1230 mentions Skopje, Prilep and Devol – acquisitions effectively barring the Serbians fromMacedonia – and even Thessaloniki, but no Adriatic port is mentioned there.55 In any case, the text of this agreement attests a revival of trans-Balkan trade to the advantage of one of the Slav powers, as economic facts caught up with military ones.56 This also helped to counterbalance the overweening Italian presence in the region’s trade.57 George Akropolites paints quite a favourable picture of Ivan Asen’s attitude towards his Greek subjects, although this was probably coloured by Akropolites’ desire to cast his bˆete noire, Theodore Angelos, in the worst possible light. However, Ivan avoided Kalojan’s mistakes and he does seem to have been regarded favourably by his new subjects; Ivan’s recently acquired title ‘tsar of the Bulgarians and of the Greeks’ offered them a guarantee of sorts.58 He hoped to give this title further substance by conquering Constantinople from the Latins. Just after his victory at Klokotnitsa in 1230, Ivan visited Mount Athos and showered gifts upon its monasteries: a symbolic expression of his role as supposed successor to the Byzantine emperors.59 His conquests also enabled him to intervene in the affairs of Serbia, a potent rival whose alliance with Epiros he found hard to forgive. Bulgarian operations led to the downfall of the Serbian ruler Stefan Radoslav,60 who had withdrawn to Dubrovnik, and then to Dyrrachium.61 However, Ivan was a realist and knew he could not take Constantinople on his own. He therefore put together a league of orthodox potentates, including John III Vatatzes, emperor of Nicaea (1221–54), and even Theodore’s brother Manuel Angelos (1230–37), emperor at Thessaloniki. Manuel was Ivan’s faithless son-in-law and in 1232 he had abandoned plans for church union with Rome and with Frederick II.62 This league gave Ivan the chance to renounce Kalojan’s nominal allegiance to the pope, and he hoped for an immediate dividend, the transformation of the Bulgarian church into a full patriarchate. It is likely that, from 1233, relations with Nicaea were close enough to force the ‘unionist’ archbishop of T’rnovo to abandon his see and retire to Mount Athos; presumably he had been induced to return to orthodoxy by the patriarch of Nicaea.63 In spring 1235, the Graeco-Bulgarian alliance was further strengthened at Gallipoli by the betrothal of the future Theodore II Laskaris (1254–58) to Ivan II Asen’s daughter, who had previously been betrothed to Baldwin II.64 After lengthy negotiations with the patriarchs of Nicaea and the east,65 the alliance was reinforced by the formal recognition of the new Bulgarian head churchman, Ioakim, as patriarch; Ioakim went to Nicaea for his consecration.66 However, for the Bulgarians the problem was that this alliance would clearly involve abandoning any claim to the Byzantine throne; part of the price for the patriarchal title was Ivan’s renunciation of his patronage over Mount Athos.67 From this point on, the attitude of the Bulgarians becomes rather erratic; Ivan Asen had probably not become Vatatzes’ ally simply in order to acquire a patriarchate, and he must have been aware of the dangers Nicaea posed to him. After an abortive joint siege of Latin-held Constantinople in 1235– 6, Ivan performed an about-turn and entered into an alliance with the Latins. He broke with Nicaea at the end of 1237, after a terrible pestilence at T’rnovo which carried off his wife and one of his children, as well as Patriarch Ioakim. Ivan believed that he was being punished for breaking his word; Bulgarian writings of this period are full of eschatological references to brilliant triumphs, but also to cautionary punishment for sins.68 As if to confirm all these prophecies, Ivan himself died in 1241. Soon afterwards the Bulgarian lands were ravaged by a terrible Mongol and Cuman army, putting paid to imperial ambitions for a long time. Nicaea stood to benefit from the settlement of numerous Cumans on the frontiers of Asia and Europe,69 seeing that the outer fringes of Bulgaria became very vulnerable. The population in Byzantino-Bulgarian borderlands such as the Rhodope range was in fact mostly Bulgarian, ready to assist any action by fellow Bulgarians, as it did after the death of John III Vatatzes in 1254, with longterm consequences.