What marked the start of NATO’s transformation from a purely defensive alliance into a large, coordinated, and powerful military force operating beyond its members’ borders...? Mcqs

What marked the start of NATO’s transformation from a purely defensive alliance into a large, coordinated, and powerful military force operating beyond its members’ borders...?

(A) Bombing campaign on Czechs

(B) Bombing campaign on Bosnian Serbs

(C) Bombing campaign on Afghanistan

(D) Bombing campaign on Iraq

Source: This question is taken from the General Knowledge (GK)