SAN FRANCISCO — Microsoft CEO Steve Ballmer isn't going to let anyone get in his way.
Not even his presumed heir apparent, who runs the software maker's Windows empire, can stop Mr. Ballmer as he pushes the company in a new direction.
That was the underlying message of a power struggle that led to the abrupt departure of Steven Sinofsky, who oversaw the Windows operating system that has been the foundation of Microsoft's success.
The fissure announced late Monday came less than three weeks after Mr. Sinofsky and Mr. Ballmer appeared on a stage in New York to hail the long-awaited release of Windows 8, a radical overhaul of the operating system. The Redmond, Wash.-based company designed it to make its products more relevant in an age when more daily computing tasks are shifting from desktop and laptop machines to smartphones and tablet computers.
Microsoft Corp. didn't elaborate on the reasons behind the end of Mr. Sinofsky's 23-year career at the company. But all signs point to tensions boiling over as Mr. Ballmer tries to weave Microsoft's products more closely together so the technology is easily accessible whenever and wherever people want to work, play and communicate.
That's a goal Microsoft rivals Apple Inc. and Google Inc. have been pursuing for the past few years, giving them a head start in a battle that's immersing technology even deeper into people's lives.
To achieve his objectives, Mr. Ballmer is trying to dismantle fiefdoms within Microsoft that date back to the 1990s, when co-founder Bill Gates ran the company. According to industry analysts, Mr. Gates divided the company into different engineering silos devoted to each of Microsoft's key franchises — Windows, the Office suite of software, online services and corporate servers. When Mr. Ballmer became CEO nearly 13 years ago, he inherited the structure and even expanded it to include new divisions to house new products such as the Xbox 360 gaming console.
Now that Mr. Ballmer is trying to tie Microsoft's operations more closely together, he is likely facing resistance from company veterans such as Mr. Sinofsky, said longtime technology analyst Rob Enderle.
"Sinofsky is an empire builder who is not going to look kindly at someone coming in and telling him he has got to start sharing," Mr. Enderle said. "But Ballmer needs everyone to do the 'Kumbaya' thing and come together. They were likely increasingly bumping heads in terms of the future of the company."
As part of Mr. Ballmer's strategy, Microsoft is expanding beyond software into device-making. The company's first tablet computer, the Surface, went on sale with the release of Windows 8 and now there is speculation that Microsoft may also make a smartphone, too. By selling hardware, Microsoft risks alienating the device manufacturers who license Windows 8.
Mr. Ballmer, 56, isn't the only to CEO facing friction within the ranks. Last month, Apple CEO Tim Cook announced he was replacing Scott Forstall, a longtime company executive in charge of the software that runs the iPhone and iPad.