More than 150 Microsoft employees signed a letter demanding the tech giant cancel a $480 million contract to build a HoloLens for the Pentagon, saying they “refuse to create technology for warfare and oppression.”

“We are alarmed that Microsoft is working to provide weapons technology to the US military, helping one country’s government ‘increase lethality’ using tools we built. We did not sign up to develop weapons and we demand a say in how our work is used,” the letter to Microsoft CEO Satya Nadella and President Brad Smith, which was posted to Twitter, states.

The employees represent the latest big tech backlash, coming from within Silicon Valley itself, as workers demand more of a say over how tech products are used and how a range of groups are treated internally.

Back in November, according to the Microsoft employees, the company awarded a major contract to the US Army with the stated objective to “rapidly develop, test and manufacture a single platform that soldiers can use to fight, rehearse and train that provides increased lethality, mobility and situational awareness necessary to achieve overmatch against our current and future adversaries.”

The workers demand that Microsoft cancel the contract, cease developing any and all weapons technologies, draft a public-facing policy around the acceptable use of such technology and appoint an independent, external ethics review board with the power to enforce compliance.

Microsoft’s HoloLens does have a range of potential applications in non-military environments, including hospitals, factories and schools.

In October, Smith published a blog in support of the tech giant’s work with the military, writing “we believe in the strong defense of the United States and we want the people who defend it to have access to the nation’s best technology, including from Microsoft.”

A number of Google employees resigned last year over that company’s Pentagon AI project, and the Mountain View, Calif., company eventually pulled out of it. A group of 450 Amazon employees in October protested against the company’s facial recognition software being sold to law enforcement.

A Microsoft spokesperson provided Fox News with the following statement on Sunday:

“We gave this issue careful consideration and outlined our perspective in an October 2018 blog. We always appreciate feedback from employees and provide many avenues for their voices to be heard. In fact, we heard from many employees throughout the fall. As we said then, we’re committed to providing our technology to the US Department of Defense, which includes the US Army under this contract. As we’ve also said, we’ll remain engaged as an active corporate citizen in addressing the important ethical and public policy issues relating to AI and the military.”