Often the trickiest onboarding challenges take place when your role changes suddenly. This happens when you are asked to pick up the pieces following another executive's sudden departure, whether he or she is your boss, peer or subordinate. This happens when you're suddenly moved to another role. This happens whenever there's a major change you had not anticipated.
In these situations, remember to prepare, react and bridge.
Ideally, you would have anticipated the possibility of something like this happening. Without knowing the exact change you were going to be surprised by, you would have your own general onboarding principles in place, based on what's worked well and less well in your previous transitions.
Whether or not you have a stand-by plan, you must pause for a moment to figure out your situation-specific plan. Sometimes it's just a moment. Sometimes it's overnight. Sometimes it's a little more time. But in any case, take some time to think through the new organization's purpose, your mission and vision, stakeholders, message and immediate communication plan. As much as you can, take control of the announcement cascade to manage the communication of your message to all the key stakeholders. (There's lots on this in that amazing book, The New Leader's 100-Day Action Plan.)
If it's a surprise, you're going to have to react. The key here is to trust your instincts and your preparation. Whatever you choose to do at first, do it with confidence. People will learn as much from your tone and manner as they will from what you actually say. Keep in mind though that everything communicates – everything you say and don't say, do and don't do.
In most cases, things won’t be as you hope they would be. Your approach should be one of bridging the gaps. Figure out what is required to deliver your mission. Figure out the brutal current reality. Put plans in place to get from the reality to your destination. Figure out the phasing of those plans so you and your teams tackle discrete pieces in the right order, generating early wins that build momentum towards your objectives.