Sentence:  The <WSD>Pechenegs</WSD> had already ceased to be a major threat by the time Kievan "Rus''' converted to Christianity in 988, and most references to them in the chronicle are in the period before this, earlier in the tenth century. 
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.