The Battle of Mesambria was a battle between the Byzantines and the Bulgarians during the war of Khan Krum. In this battle, during the night attack, the Byzantines under the command of their Emperor Leo V almost completely defeated the Bulgarians.
Sources
Wasilewski T. Historia Bułgarii. — Wrocław: Ossolineum, 1983, p. 49. — ISBN 83-0402466-7 Грего-Болгарские войны Sytin Military encyclopedia