What is the initial incident in "The Cask of Amontillado"?

In my opinion, the initial incident in this story is not
really even seen in the story.  To me, the initial incident is whatever Fortunato did in
the past to Montresor.

The initial incident is the thing
that leads to the rising action in the story.  To me, the rising action in this story is
the interaction between Montresor and Fortunato as Montresor maneuvers Fortunato into
going down into Montresor's wine cellars.

So the initial
incident has to be whatever caused this to happen.  In my opinion, that is the conflict
between them that is only referred to in this story.