Occasion

A careless remark by a diplomat during a tense negotiation is overheard by journalists. The remark itself does not start a war, but it creates a situation where trust breaks down, accusations fly, and soon both sides are preparing for conflict. The diplomat’s words did not directly cause the war, but they provided the spark that made it possible. What did the diplomat’s remark do? It occasioned a diplomatic crisis.

Cause (to directly bring about an effect or result) contrasts with occasion, which means to create a situation or opportunity where something can happen, often indirectly. Occasion focuses on providing the context or trigger, while cause is about direct, inevitable production of an outcome.