between whom did it take place?
The Byzantine Empire, led by the Emperor Alexios I Komnenos , and the Normans of southern Italy under Robert Guiscard, Duke of Apulia and Calabria.
Battle of Dyrrhachium (1081)
The Battle of Dyrrhachium took place on October 18, 1081 between the Byzantine Empire, led by the Emperor Alexios I Komnenos (r. 1081–1118), and the Normans of southern Italy under Robert Guiscard, Duke of Apulia and Calabria. 
where did the battle of dyrrhachium take place? The battle was fought outside the city of Dyrrhachium, the major Byzantine stronghold in the western Balkans, and ended in a Norman victory.
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Battle of Dyrrhachium (1081) [SEP] Introduction
The Battle of Dyrrhachium took place on October 18, 1081 between the Byzantine Empire, led by the Emperor Alexios I Komnenos (r. 1081–1118), and the Normans of southern Italy under Robert Guiscard, Duke of Apulia and Calabria. The battle was fought outside the city of Dyrrhachium (present-day Durrës in Albania), the major Byzantine stronghold in the western Balkans, and ended in a Norman victory. Following the Norman conquest of Byzantine Italy and Saracen Sicily, the Byzantine emperor, Michael VII Doukas (r. 1071–1078), betrothed his son to Robert Guiscard's daughter. When Michael was deposed, Robert took this as an excuse to invade the Byzantine Empire in 1081.