A year of turmoil and turnover

Volkswagen's emissions scandal forced the departure of several key executives, pushed others into new roles and brought new leadership for North America.

Martin Winterkorn: Days after the scandal erupted, a "stunned" and "shocked" Winterkorn resigned as CEO of Volkswagen AG, saying he was accepting responsibility for the diesel mess but denying any wrongdoing. Winterkorn -- who survived a clash earlier in the year with then-Chairman Ferdinand Piech -- had led VW through an aggressive expansion that put it in position to overtake Toyota Motor Corp. as the industry's global leader. Porsche boss Matthias Mueller took his place.

Michael Horn: The CEO of Volkswagen Group of America and the public face of VW in the U.S., Horn was the one left to address reporters at a vehicle unveiling days after the diesel scandal became public. He left in March by way of "mutual agreement" -- but not before voicing his frustration with VW management, declaring in an October congressional hearing: "This company has to bloody learn." His exit drew an outcry from dealers, who hailed his candor and work to rebuild frayed factory-dealer relations.

Joerg Sommer: VW of America's product planning chief parted ways with the automaker in August after roughly three years in that role. Sommer, an expert in electric vehicles, earlier was head of electric mobility sales and marketing for VW Group. VW declined to elaborate on Sommer's departure when it was disclosed. Sommer has since been named a marketing VP at startup Faraday Future.

Heinz-Jakob Neusser: The group's head of powertrain development since 2012, Neusser later assumed overall responsibility for r&d at the VW brand until he was put on involuntary leave in connection with the diesel emissions scandal and replaced in December by his Skoda counterpart, Frank Welsch.

Ulrich Hackenberg: The Audi r&d chief was Winterkorn's most trusted engineer and the father of the modular architecture strategy. Before being parachuted into Audi in July 2013 to spark innovation at the luxury arm, he headed r&d at the VW brand. He left the board in December and was replaced the following month by his powertrain chief, Stefan Knirsch.

Wolfgang Hatz: The Porsche r&d chief served as VW Group's head of powertrain development from 2007 until 2012. His close ties to now-VW CEO Matthias Mueller gave him a long reprieve, and Porsche executives said they hoped to keep him, but he, too, had to leave in May. Michael Steiner took up his responsibility.

Winfried Vahland: Vahland, who led a turnaround of VW's China business and later its Skoda unit, was to have headed a newly created North America region for the automaker starting in November 2015, under a plan developed before the scandal broke. But he balked at the post and quit VW following Winterkorn's departure. Vahland had been a contender to succeed Winterkorn.

Hinrich Woebcken: The former BMW purchasing executive was tapped to run VW's new North America region for all brand operations on Jan. 19 and assumed the post on April 1. He also was named CEO of VW Group of America on April 15 after serving as interim chief following Horn's departure, assuming responsibility for all VW Group brands and its North American factories.

David Detweiler: As part of a shake-up of its legal team, VW Group of America named Detweiler general counsel and executive vice president in February. Detweiler had worked at international law firm Clifford Chance in Frankfurt, where he had advised VW on a $2.8 billion bond deal.

Christine Hohmann-Dennhardt: A former justice in Germany's highest court, she served as head of integrity and legal affairs for Daimler, where her chief responsibility was to help manage and clean up a bribery scandal. She switched to Volkswagen in January with Daimler's consent.

Mark Barnes: Barnes was reassigned to COO of Bentley of the Americas in March after more than two years as the VW brand's U.S. sales chief.

David Geanacopoulos: After nearly eight years as VW Group of America's top lawyer, Geanacopoulos was reassigned to a new post as part of Detweiler's hiring: senior executive vice president for public affairs and public policy. His mission: "to help us begin to rebuild the trust we have lost," Horn said upon the appointment.

Matthias Mueller: The head of Porsche rose to the group CEO position, succeeding Winterkorn, as part of the September 2015, shake-up that accelerated a long-planned restructuring of the company's brand and regional divisions. In outlining his strategic plan this year, Mueller said the company suffered over the years from a "fixation on size."

Ron Stach: The former head of VW's South Central Region was promoted to U.S. sales chief of the VW brand in March, succeeding Barnes.

Hendrik Muth: The former head of VW's high-performance division and its U.S. vehicle pricing chief succeeded Sommer as VW of America's vice president of product marketing and strategy. He joined VW in 2012.

Frank Witter: The former CEO of Volkswagen's captive finance arm became CFO of VW AG in October, succeeding Hans Dieter Poetsch, who was elevated to chairman of the supervisory board at the direct bidding of the Porsche and Piech clans.