The Battle of Pliska or Battle of Vărbitsa Pass is a series of battles between troops, gathered from all parts of the Byzantine Empire, led by the Emperor Nicephorus I Genik, and Bulgaria, governed by Khan Krum.

The Byzantines plunder and burn the Bulgar capital Pliska, which gives time for the Bulgarians to block passes in the Balkan Mountains that served as exits out of Bulgaria.

The final battle takes place on 26 July 811, in some of the passes in the eastern part of the Balkan, most probably the Vărbitsa Pass.

Here, the Bulgarians use the tactics of ambush and surprise night attack to effectively trap and immobilize the Byzantine forces, thus annihilating almost the whole army, including the Emperor.

After the battle, Krum encases Nicephorus's skull in silver, and uses it as a cup for wine-drinking.

This is probably the best documented instance of the custom of the skull cup.The battle of Pliska is one of the worst defeats in Byzantine history.

It deters Byzantine rulers from sending their troops north of the Balkans for more than 150 years afterwards, which increases the influence and spread of the Bulgarians to the west and south of the Balkan Peninsula, resulting in a great territorial enlargement of the First Bulgarian Empire.