I characterize the incentives to undertake strategic investments in markets with Nash competition and endogenous entry. Contrary to the case with an exogenous number of firms, when the investment increases marginal profitability, only a “top dog” strategy is optimal. For instance, under both quantity and price competition, a market leader overinvests in cost reductions and overproduces complement products. The purpose of the strategic investment is to allow the firm to be more aggressive in the market and to reduce its price below those of other firms. Contrary to the post-Chicago approach, this shows that aggressive pricing strategies are not necessarily associated with exclusionary purposes.