Bertelsmann Chairman and CEO Hartmut Ostrowski is resigning from his position effective at yearend, the company announced Monday.

Bertelsmann owes Hartmut Ostrowski a great debt of gratitude, Gunter Thielen, chairman of the supervisory board, said in a statement put out by the company. He led the company in difficult times. I look forward to continuing to work with him on the Supervisory Board. The timing of the changeover ensures that the passing of the baton to Thomas Rabe will be handled smoothly.

Ostrowski, 53 years old, is leaving the company for personal reasons and will move to the supervisory board. The company said the changeover takes place amicably and by mutual consent.

Chief Financial Officer Thomas Rabe, 46, will take over as Chairman and CEO.

 The shareholders and Supervisory Board wish Thomas Rabe the best of success in his new role, Thielen said. We are sure that in him, we have an entrepreneur at the top who will lend further momentum to Bertelsmann's growth strategy and future development.

This move comes as a surprise to some. The New York Times reports that until the announcement, many analysts predicted that Ostrowski would be given another term as CEO, due to his success steering the company through the financial crisis.

The Gutersloh, Germany based media conglomerate has a wide variety of holdings in television, publishing, and outsourcing services. In 2010, the company employed 100,000 people and generated revenue of € 15.8 million ($21.5 million).

Write to Samuel Weigley at s.weigley@ibtimes.com