look ahead and reason back."

In your Managerial Economics textbook, we consider a sequential-move game in which an entrant is considering entering an industry in competition with an incumbent firm . There are several possibilities of how this sequential game will be played. We want to use the Froeb rule of "look ahead and reason back."
Can, and how does, the entrant succeed? Is the incumbent ever in control of this game?
You may wish to review the old game known as Duopoly, as well as Antoine-Augustin Cournot, to help inform your post.