Final answer:
The initial cause of the conflict between Serbs and Kosovo Albanians was rooted in ethnic tensions and Kosovo Albanians' desire for independence, leading to the involvement of Slobodan Milošević's forces and NATO's intervention.
Step-by-step explanation:
The initial cause of the conflict between Serbs and Kosovo Albanians (represented by CK and MS in the question) was rooted in ethnic tensions and the push for independence by Kosovo Albanians. The Kosovo Liberation Army (KLA) sought an independent Kosovo and an alliance with Albania, opposing the Serb power structure. In response, Slobodan Milošević sent troops to confront the KLA in 1998, escalating into a civil war. The situation deteriorated with reciprocal atrocities leading to a massive humanitarian crisis and NATO intervention in 1999 to halt the ethnic cleansing and violence.