Microsoft announced it will be cutting up to 18,000 jobs over the next year; the biggest job cuts in the company’s history. The layoffs are part of a plan to re-align itself after its acquisition of Nokia in April. 

Microsoft CEO Satya Nadella broke the news in an all-staff email, saying the layoffs are necessary to streamline the company. 

“We plan to have fewer layers of management, both top down and sideways, to accelerate the flow of information and decision making. This includes flattening organizations and increasing the span of control of people managers,” Nadella writes.

The move comes as Microsoft tries to shift more of its business toward cloud and mobile computing, as well as become more efficient.

“People view Microsoft as being sluggish,” says Colin Gillis, a senior tech analyst at BGC Financial. “The new management want to change that and change the culture. We’ll see how this works.”

Gillis says two thirds of the workers losing their jobs are former Nokia employees who became part of Microsoft after the companies merged. According to the announcement, the layoffs will mostly be complete by the end of this year.