General Motors surprised the automotive world this morning, announcing Chairman and CEO Dan Akerson would step down Jan. 15, and naming global product-development and purchasing chief Mary Barra the first woman to head a major U.S. automaker.

GM says Akerson, 65, decided to pull ahead his retirement by several months after his wife recently was diagnosed with an advanced stage of cancer.

The decision to appoint Barra, 51, as the next CEO marks the culmination of a meteoric rise and represents a signature move for Akerson, who has stressed new thinking at the post-bankruptcy GM since taking over the reins from Ed Whitacre in September 2010.

Akerson may have been signaling the GM board’s path this summer when he predicted a woman eventually would fill the CEO’s chair.

Just two years ago, 33-year GM veteran Barra was in charge of the human resources department when she was plucked from relative obscurity by Akerson to take over global engineering. She continued to advance after that, being named to the Adam Opel advisory board in January 2012 and tapped as the head of global purchasing and supply chain last August.

In its statement announcing the move, which comes a day after U.S. government sold the last of its remaining shares in the company, GM credits her with leading the company’s ongoing turnaround, revitalizing its product-development process and delivering record product-quality ratings and higher customer satisfaction.

“With an amazing portfolio of cars and trucks and the strongest financial performance in our recent history, this is an exciting time at today’s GM,” Barra says in a statement. “I’m honored to lead the best team in the business and to keep our momentum at full speed.”

Although Barra will join the board, the chairman slot will be filled by non-executive Theodore (Tim) Solso, 66, a former chairman and CEO of Cummins who has been on the GM board since June 2012.

Akerson has said from the moment he took the job that he wouldn’t stay long as CEO, and over the past year Barra was seen part of a four-person race to succeed him that included North America President Mark Reuss, Chief Financial Officer Dan Ammann and Vice Chairman Steve Girsky, who has been overseeing restructuring in Europe.

All of those players are being affected by the elevation of Barra in some way.

Reuss, 50, will take over as executive vice president-Global Product Development, Purchasing and Supply Chain.

“The driver’s seat of designing and engineering the strongest product line up in GM’s history is the best seat to have,” he says in a statement. “We’re going to keep the pedal down on GM’s product resurgence and keep winning new customers.”

Ammann, 41, steps up to GM president, where he will oversee the company’s regional operations around the world. The global Chevrolet and Cadillac brand organizations and GM Financial also will report to Ammann.

“We have a significant opportunity to further integrate and optimize our operations to deliver even better results,” he says. “While we have made good progress, we still have much work ahead of us to realize GM’s full potential.”

Girsky, 51, will shift into a senior advisory role until he steps aside in April. He will remain on the board of directors, however.

Reuss’ slot as president of North America will be filled by Alan Batey, 50, currently head of Global Chevrolet and U.S. Sales and Marketing operations. He will advance to executive vice president as part of the move. GM has not named a replacement for Batey.

Akerson says his goals were to “put the customer at the center of every decision we make, to position GM for long-term success and to make GM a company that America can be proud of again. We are well down that path, and I’m certain that our new team will keep us moving in that direction.”

dzoia@wardsauto.com