At least 50 Microsoft employees have requested the company back to deal with the US military to provide augmented reality technology.
In particular, the group has said the firm's headset, HoloLens, must not be used to "help people kill ".
In November, Microsoft agreed to pay $ 479m (£ 367m) to develop a platform that would use about 1
"A Microsoft spokesperson said."
A letter sent by Microsoft across the UK has been posted by employees across multiple departments
"Microsoft must stop in its activities to empower the US Army's ability to cause harm and violence," it reads.
- HoloLens, first released to developers in March 2016 allows the wearer to see digital images laid out over the real world. Microsoft's chief executive Satya Nadella is due to announce HoloLens 2 at Barcelona event on Sunday, ahead of the Mobile World Congress trade show.
The letter demands Microsoft cancel the Integrated Visual Augmentation System (IVAS) contract, stop developing "any and all" weapons technologies, and draft a public policy statement on the matter.
It would call for an "independent, external ethics review board" that would oversee compliance with that policy.
It is not the first time that Microsoft employees have spoken out against the firm's work with government entities.
In June, with the Trump administration mired in controversy over family separations on the US-Mexico border, the firm provided the services to the US Immigration and Customs Enforcement Agency (ICE).
Mr Nadella eventually denounced the White House's actions and said Microsoft's technology was used for standard office-related tasks.
With this latest employee rebellion, Microsoft does not have to seek easy defense. According to the contract, the goal is to "increase lethality by enhancing the ability to detect and decide before the enemy".
Microsoft is understood to have outbid rival augmented reality developers, such as Magic Leap.
Microsoft's president and top lawyer Brad Smith has said he is not happy with the nature of the military work. However, in the latest letter, employees said that suggestion was flawed.
"Microsoft fails to inform engineers on the intent of the software they are building.
"There are many engineers who have contributed to the construction of a car in front of them, who would like to help them
"These engineers have now lost their ability to make decisions about what they've been working on, rather than just implicitly being profiteers."
- Could HoloLens tech help save babies' lives?
Microsoft is not the only company to face internal anger over military work. Last year, Google did not renew a contract with the US on Project Maven, an artificial intelligence program in development with the Pentagon.
However, Amazon's chief executive Jeff Bezos said he would enthusiastically work with the military.
"This is a great country – it needs to be defended"
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