To integrate companies following a merger, arguably the most important challenges involve the top of the organization—appointing the right top team, structuring it appropriately, defining its agenda, and building the trust that enables its members to work well together. Executives who fail to overcome these challenges are responsible for the ego clashes and politics that are often the root cause of spectacular failed mergers.

Unfortunately, recent thinking about change management no longer emphasizes the pivotal role of the top team. The consensus on how to manage change has shifted to a dispersed approach because too many initiatives designed to cascade down the hierarchy have delivered disappointing results. The usual interpretation is that top-down change fails because at every step messages get diluted, so that each succeeding one seems less compelling and less authentic.

While this may be true in certain circumstances, a merger requires direction from the top because that is the only way to initiate change throughout an organization. The change required to integrate companies cannot be driven from an entrepreneurial business unit, an innovative functional unit, or the front line. Too much coordinated, programmatic change must be achieved in too short a time for such approaches to succeed....