This paper analyzes two takeover methods that exist in the corporate acquisition market: tender offers and mergers. Tender offers are analyzed as an English auction in which the target firm serves as the auctioneer and the bidding firms serve as bidders, while mergers are analyzed using a Nash bargaining model between the target firm's management and the acquiring firm's management. The two acquisition methods differ in terms of the negotiating parties, the differing bargaining positions of target firm shareholders and target firm management, the degree of competition, management resistance, and information, and under these characteristics, the acquiring firm selects one of the two acquisition methods based on its synergy gains. This paper also analyzes the effects of the target firm management's role in acquisition attempts and the competitive entry costs that exist in tender offers on the acquiring firm's choice of acquisition method. In the base model where competitive entry costs do not exist and management defense strategies are not employed during tender offers, the initial synergy-discovering acquiring firm chooses a tender offer when synergy gains are very low, a merger when synergy gains are at intermediate levels, and a tender offer when synergy gains are very high. This conclusion is derived when the target firm management's bargaining power and the reserve price for the target firm's stock are not excessively high. If the target firm management's bargaining power and reserve price are very high, the acquiring firm will acquire the target firm only through tender offers regardless of the size of synergy gains. When management employs defense strategies against tender offers, acquiring firms with synergy gains lower than the target firm management's reserve price become unable to acquire the target firm. Another major conclusion derived in this paper is that when the management's reserve price is below a certain value, management resistance can increase the expected returns for target firm shareholders. When competitive entry costs such as information investigation costs exist, preemptive bidding increases the expected returns of the initial synergy-discovering firm.