Sentence:  The siege of Dristra failed, as the emperor found himself surrounded by the <WSD>Pechenegs</WSD>....Fearing a Cuman–Pecheneg alliance, Alexios immediately sued for peace and the <WSD>Pechenegs</WSD> agreed to a truce, which they immediately broke in order to take advantage of Alexios' notorious lack of troops and invade Thrace. 
Meaning of the word marked with <WSD> tags:  A member of a specific semi-nomadic Turkic people from central Asia, some of whom migrated into eastern Europe.