Simeon I of Bulgaria nearly conquered Constantinople, but lacked the ships to finish it.
Between 913 and 927, the Bulgarian Empire dominated the Balkans, crushing Byzantine armies and annexing Serbia. Tsar Simeon I aimed to seize the Byzantine throne itself, but his land-based military might could not overcome the impregnable walls of Constantinople without a navy, leading to a desperate, failed alliance with North African caliphs.
The conflict began in 913 when the Byzantine emperor Alexander abruptly ceased annual tribute payments to Bulgaria. Simeon I, an educated ruler who had studied in Constantinople, viewed this as a casus belli. He marched on the Byzantine capital, forcing the regency to crown him 'Emperor of the Bulgarians' in a ceremony that signaled his ambition to create a joint Bulgarian-Roman state. However, a palace coup in 914 by Empress Zoe Karbonopsina revoked these concessions, reigniting a war that would last over a decade.
Bulgarian military supremacy was cemented in 917 at the Battle of Achelous, where Simeon’s forces annihilated the Byzantine army. Following this, the Bulgarians captured key cities like Adrianople and Thebes, and even reached the Isthmus of Corinth. Despite these victories, Simeon realized that Constantinople was impenetrable to land forces alone. He attempted to secure a maritime alliance with the Fatimid Caliph Ubayd Allah al-Mahdi Billah in 922, proposing a joint siege where the Bulgarians would take the city and the Fatimids would claim Byzantine territories in Italy. The plan collapsed when Byzantine forces intercepted the envoys near the Calabrian coast.
By 927, both empires were economically and militarily exhausted. Simeon died in May 927, and his successor, Peter, negotiated a peace treaty that recognized the Bulgarian ruler as emperor and the Bulgarian Orthodox Church as an independent patriarchate. This treaty, sealed by a marriage between Peter and Romanos I Lekapenos's granddaughter Irene, established 40 years of stability. While Simeon failed to capture Constantinople, his reign transformed Bulgaria into the literary and spiritual center of Slavic Europe, marked by the invention of the Cyrillic alphabet by Clement of Ohrid.
