More than 225 Google engineers and other workers have formed a union, the group revealed Monday, capping years of growing activism at one of the world’s largest companies and presenting a rare beachhead for labor organizers in staunchly anti-union Silicon Valley.

The union’s creation is highly unusual for the tech industry, which has long resisted efforts to organize its largely white-collar workforce. It follows increasing demands by employees at Google for policy overhauls on pay, harassment and ethics, and is likely to escalate tensions with top leadership.

The new union, called the Alphabet Workers Union after Google’s parent company, Alphabet, was organized in secret for the better part of a year and elected its leadership last month. The group is affiliated with the Communications Workers of America, a union that represents workers in telecommunications and media in the United States and Canada.