We analyze the incentives of a controlling shareholder of a firm to acquire, directly or indirectly through his firm, shares in a competitor. We charaterize the conditions under which these partial acquisitions are profitable for this dominant shareholder as well as the equilibrium toehold and its nature: controlling or silent. We find that while this shareholder gains, the acquisition is detrimental to minority shareholders of his firm, or of the target, or even of both. We show that the incentives are enhanced if the dominant shareholder initially holds silent stakes in rivals while controlling interests may discourage them. Moreover, we find that partial acquisitions always lead to a decrease in the joint profit of the two firms involved, and an increase in competitors's profits as the market becomes less competitive.