In 922 the Bulgarians continued their successful campaigns in Byzantine Thrace, capturing a number of towns and fortresses, including Adrianople, Thrace's most important city, and Bizye. In June 922 they engaged and defeated yet another Byzantine army at Constantinople, confirming the Bulgarian domination of the Balkans. However, Constantinople itself remained outside their reach, because Bulgaria lacked the naval power to launch a successful siege. The attempts of the Bulgarian emperor Simeon I to negotiate a joint Bulgarian–Arab assault on the city with the Fatimids were uncovered by the Byzantine and countered.