Thousands of Google employees are demanding that the company pull out of a controversial AI project that would help the Pentagon identify video images and possibly improve the U.S. military’s use of drone strikes.

In a letter signed by some 3,100 Googlers, including senior-level engineers, employees said the project—called Project Maven—flies in the face of the company’s famous “Don’t Be Evil” mantra, the New York Times reports. The letter, addressed to Google CEO Sundar Pichai, further suggests that the project will hurt Google’s brand and make it harder for the company to retain top talent.

It’s also just the wrong thing to do, they add. “We believe that Google should not be in the business of war,” the letter states.

Google has described the project as “non-offensive,” but in a statement to the Times, Pichai acknowledged that the use of AI in warfare raises valid concerns. He said the company is actively engaged in “comprehensive discussion” on the topic.