VII, and Lekapenos assumed the new title basileopator. On 24 September 920, he was named caesar; and on 17 December, Romanos was crowned senior emperor. In subsequent years Romanos crowned his own sons co-emperors, Christopher in 921, Stephen and Constantine in 924, although, for the time being, Constantine VII was regarded as first in rank after Romanos himself. It is notable that, as he left Constantine VII untouched, he was called 'the gentle usurper'. Romanos strengthened his position by marrying his daughters to members of the powerful aristocratic families of Argyros and Mouseles, by recalling the deposed patriarch Nicholas Mystikos, and by putting an end to the conflict with the Papacy over the four marriages of Emperor Leo VI. His early reign saw several conspiracies to topple him, which led to the successive dismissal of his first paradynasteuontes, John the Rhaiktor and John Mystikos. From 925 and until the end of his reign, the post was occupied by the chamberlain Theophanes. War and peace with Bulgaria The first major challenge faced by the new emperor was the war with Bulgaria, which had been re-ignited by the regency of Zoe. The rise to power of Romanos had curtailed the plans of Simeon I of Bulgaria for a marital alliance with Constantine VII, and Romanos was determined to deny the unpopular concession of imperial recognition to Simeon, which had already toppled two imperial governments. Consequently, the first four years of Romanos' reign were spent in warfare against Bulgaria. Although Simeon generally had the upper hand, he was unable to gain a decisive advantage because of the impregnability of Constantinople's walls. In 924, when Simeon had once again blockaded the capital by land, Romanos succeeded in opening negotiations. Meeting Simeon in person at Kosmidion, Romanos criticized Simeon's disregard for tradition and Orthodox Christian brotherhood and supposedly shamed him into coming to terms and lifting the siege. In reality, this was accomplished by Romanos' tacit recognition of Simeon as emperor of Bulgaria. Relations were subsequently marred by continued wrangling over titles (Simeon called himself emperor of the Romans as well), but peace had been effectively established. On the death of Simeon in May 927, Bulgaria's new emperor, Peter I, made a show of force by invading Byzantine Thrace, but he showed himself ready to negotiate for a more permanent peace. Romanos seized the occasion and proposed a marriage alliance between the imperial houses of