  Motivation: How immature teams can become agile is a question that puzzles
practitioners and researchers alike. Scrum is one method that supports agile
working. Empirical research on the Scrum Master role remains scarce and reveals
contradicting results. While the Scrum Master role is often centred on one
person in rather immature teams, the role is expected to be shared among
multiple members in mature teams. Objective: Therefore, we aim to understand
how the Scrum Master role changes while the team matures. Method: We applied
Grounded Theory and conducted qualitative interviews with 53 practitioners of
29 software and non-software project teams from Robert Bosch GmbH. Results: We
discovered that Scrum Masters initially plays nine leadership roles which they
transfer to the team while it matures. Roles can be transferred by providing a
leadership gap, which allows team members to take on a leadership role, and by
providing an internal team environment with communication on equal terms,
psychological safety, transparency, shared understanding, shared purpose and
self-efficacy. Conclusion: The Scrum Master role changes while the team
matures. Trust and freedom to take over a leadership role in teams are
essential enablers. Our results support practitioners in implementing agile
teams in established companies.
