A sub game excellent Nash equilibrium is an equilibrium such that players' methods represent a Nash equilibrium in each sub game of the initial game. it should be found by backward induction, an iterative method for solving finite in depth kind or sequential games. First, one determines the optimal strategy of the player who makes the last move of the sport. Then, the optimal action of the next-to-last moving player is decided taking the last player's action as given. the method continues during this manner backwards in time till all players' actions are determined.
Sub game excellent equilibria eliminate no credible threats.