敵意併購在第4 波的併購風潮相當盛行。目標公司面對敵意併購的威脅必須思考如何來對付。其中引進白衣武士(盟友) 來扮演友善併購者是一種防禦方法之一。然而這種做法是否符合股東利益極大化或是與管理者利益鞏固假說，這是值得探討的議題。本研究以1980 至2007 年間所發生的323 件敵意併購中，依據有無引進白衣武士，並將有引進白衣武士的子樣本中再分成由白衣武士成功併購與原敵意併購者贏得併購等共分三群來研究，結果發現白衣武士的救援事實上無法支持股東利益假說；同時結果也顯示交易條件並沒有顯著有利於目標公司。

The unique characteristic of the Fourth Merger Wave plays a significant role in hostile mergers. Firms that become targets of a hostile bid need to resist actively their raiders. For these targeted firms, seeking a friendly bidder or a white knight is an alternative approach to hostile acquirer attacks. However, it is uncertain if this move corresponds to the “shareholder interest hypothesis”or the“management entrenchment hypothesis.”This paper examines these two competing hypotheses by analyzing data gathered from 323 global events of successful hostile takeovers covering the period 1980-2007, the focus of which is on the utilization of white knights against hostile takeovers. The collected sample is divided into three case groups: successful white knights, successful hostile bidders competing with white knights, and successful hostile bidders without white knights. Results show that the managerial entrenchment hypothesis is more appropriate compared with the shareholder interest hypothesis. From a conceptual perspective, this suggests that dealings can benefit target firms. Nevertheless, the results may also be insignificant.