Leaders must be visible and vocal about the culture they want for the organization. And because having the right culture is especially important in turbulent times (mergers, acquisitions, etc.), leaders should communicate even more about the expected behaviors during those times.
Unfortunately, turbulent times tend to distract executives from the culture message. All the attention goes to tactical performance and to processes. The focus shifts to rules and away from values. Turbulent times are the worst times to shift focus because they breed situations not covered by existing rules. When employees have no rules to help them make decisions, they are supposed to turn to values and culture.
If you are planning a big change in your organization, put culture management at the top of your to-do list.