Question: What did the Pecheneg frequesntly do over the span of two centuries?
Sentence: For over two centuries they launched sporadic raids into the lands of Rus′, which sometimes escalated into full-scale wars (such as the 920 war on the Pechenegs by Igor of Kiev reported in the Primary Chronicle), but there were also temporary military alliances (e.g. the 943 Byzantine campaign by Igor).
Answer in sentence: yes