And Stalin collaborated with the Nazis until 1942.
This was not about sweetness and light - the war in the Balkans was a total and bloody struggle for power, and each player knew that if he did not win - or side with the winner - he would eventually be shot.
It was not clear whether the Axis or the Alliance would triumph - and in the event of an Allied triumph it was not clear whether it would be the Western half or the Soviet half that would control the Balkans.
Everyone caught in the storm hedged their bets.
Set Stalin aside.
The Germans turned on Mihailovic when Gen. Simovic described him as the “Commander of all Yugoslav armed forces that are fighting in the country…” in late 1942.
For three years (1942-45), both Mihailovic and Tito moved their forces across NDH territories locked in combat with one another, with the Germans, with the Italians, with the Ustashas, or in some triangular form.
Point being, is that there was a Civil War going on in the Balkans within a broader World War (II)----This point often gets missed around here.