Kara Swisher reported in Re/code this week that Yahoo CEO Marissa Mayer asked her top executives to make explicit commitments to stay at Yahoo – that they take a “pledge.” Swisher writes: “That move seems to have backfired a bit, resulting in several major departures recently, including European boss Dawn Airey, marketing and media head Kathy Savitt, development chief Jackie Reses and many others to other jobs.” (Mayer herself had earlier claimed on Yahoo’s third quarter earnings call that the departures were carefully planned.)

While it’s probably true that Mayer didn’t ask for a pledge expecting Airey, Savitt, and Reses to depart, we disagree that the pledge “backfired.” Managers and employees have to build relationships based on trust and clear expectations, especially when an organization is going through significant changes. And that’s even more true of an executive or management team. Good managers know that it’s difficult to achieve long-term success without obtaining long-term commitments from employees.

By setting the explicit expectation that Yahoo executives needed to commit to sticking around through a 3 to 5 year tour of duty to turn around the company, Mayer will be able to build much stronger relationships with the far greater number of top executives who decided to take the pledge.

Consider the alternative: What if Mayer launched her new turnaround plan without speaking with her top executives about their own plans? Rather than having the time to find the right replacements, Mayer might have been forced to deal with replacing Yahoo’s European boss, marketing and media head, and development chief while in the middle of a complex transition. Before you begin an effort like this, you have to know that the whole team is ready to move forward together, with focus and concentration. They have to be all in.

Worse, what if she hadn’t had this conversation, and her executives stayed on, halfheartedly carrying out their duties while spending the other half of their time exploring their next moves? In a high-performance organization, a partial commitment is worse than none at all.

Far too many managers seem to think that ignorance is bliss, and that as long as their employees haven’t announced plans to leave, they’re planning to stay indefinitely. A far better approach is to define a explicit tour of duty to which both parties commit. Not only does this honest conversation allow a greater degree of trust, knowing when such a tour is drawing to a close allows managers to proactively define the next commitment necessary for each valuable employee.

Airey, Savitt, and Reses had all spent several years at Yahoo working with Mayer; enough time had passed for them to complete an initial tour of duty. Mayer was right to work with them on defining a new tour of duty, even if ultimately they couldn’t find one that made sense for both sides.

Like Mayer’s pledge, these tours of duty are moral commitments, not legal contracts. Yet by creating an environment where managers and employees can truly be allies, these moral commitments translate into better business performance.