The leader strategy is divided into two distinct strategies: on the one hand we have the offensive strategy, where the leader seeks to dominate its market. On the other hand, we have a defensive strategy, the leader seeks to protect its market share and competitors. 1) We divide the defensive strategy into 6 different categories.- the positioning defense strategy: this is the outpost strategy; - the preventive strategy: act rather than react, the strategy of the counter-offensive approach: we fight our competitor on our own ground; - The mobile defense strategy: this strategy is based on market diversification and expansion, - The strategic withdrawal strategy: the company focuses on certain segments and abandons weak segments.2) The Challenger Strategy Challenger strategy seeks to eliminate the weakest or attack the market leaders. Five approaches are possible: - the frontal attack: the most costly strategy which operates through prices, - The side attack: it consists of taking advantage of a weakness of its competitor, - Encirclement: it is attack on several weak points of its competitors, - guerrilla warfare: the objective is to attack the competitor on its specific products.