SAN FRANCISCO — More than 100 employees at Google signed a petition this week calling on the tech giant to “refuse to comply” with the Pentagon on some uses of artificial intelligence in military operations.

Employees at Amazon, Google and Microsoft urged their leaders in a separate open letter Thursday to “hold the line” against the Pentagon.

And technologists at companies across Silicon Valley said that AI should not be used for purposes such as mass surveillance of Americans.

Silicon Valley has rallied behind the AI startup Anthropic over its dispute with President Donald Trump and the Pentagon about how its technology may be used for military purposes. Dario Amodei, Anthropic’s CEO, has said he does not want the company’s AI to be used to surveil Americans or in autonomous weapons, saying this could “undermine, rather than defend, democratic values.”

Trump and his officials, in contrast, want the military to use whatever AI it buys however it wants, as long as it complies with the law. On Friday, Trump called Anthropic a “radical Left AI company run by people who have no idea what the real World is all about,” and Defense Secretary Pete Hegseth labeled the startup a “supply chain risk,” a move that would sever ties between the company and the U.S. government.

Now what began as a whisper of support for Anthropic in the tech industry has crescendoed into a shout. The support — voiced by top leaders at Anthropic’s rivals, as well as rank-and-file engineers at Google and other large companies — stood out because Silicon Valley had largely appeared to be in lockstep with the Trump administration.

But the Pentagon’s actions appear to have driven a wedge between Washington and Silicon Valley. Coalescing behind Anthropic was in many ways a throwback to a pre-Trump Silicon Valley, when tech workers often spoke up against what they viewed as dangerous or inappropriate uses of powerful technologies that they had worked on.

“Now it is like we are going back to a time about eight years ago,” said Jack Poulson, one of the employees who protested Google’s work with the military in 2017. “There is a lot more activism now.”

The rallying behind Anthropic was tinged with opportunism. Sam Altman, the chief executive of OpenAI, said in a memo to employees this week that “we have long believed that AI should not be used for mass surveillance or autonomous lethal weapons,” which is the same stance as Anthropic’s.

But late Friday, after Trump had ordered federal agencies to stop using Anthropic’s technology, OpenAI said it had reached its own agreement with the Pentagon to provide its AI for classified systems. OpenAI said it had found a way to put safeguards into its technologies that would somehow prevent the systems from being used in ways that it does not want them to be.

Anthropic’s unwillingness to accede shows how the Department of Defense cannot easily force Silicon Valley firms to comply. Unlike defense contractors that have worked with the Pentagon for decades and are reliant on long-standing military contracts, the AI companies are contending with different internal pressures and external factors.

Many of them depend on highly skilled workforces of AI technologists who are hard to recruit and harder to retain. Disaffected employees can easily jump ship to other companies if they are unhappy with what they are hearing from their corporate leaders. In the last year, Meta, OpenAI, Google and others have spent millions — some say billions — of dollars to land and keep top talent.

For many AI companies, government contracts are only one piece of an expanding pipeline of business. The $200 million contract that Anthropic has been negotiating with the Pentagon for AI use in classified systems, which precipitated the fight, would most likely be only a small percentage of the company’s revenue. Anthropic primarily sells AI software to other businesses and last year hit a monthly pace of $8 billion to $10 billion in annual revenue, Amodei said in December.

Current and former defense officials said the Trump administration had misread how strongly Anthropic felt about getting assurances on how its AI would be used. Pentagon officials believed Anthropic would fall in line after they threatened to either cut the company off from government business or force it to provide its AI model without restrictions, they said.

The Pentagon and Anthropic did not respond to requests for comment.

Anthropic, Google, OpenAI and xAI have been working with the Pentagon in a pilot program to bring AI to the Defense Department. That meant that as the Pentagon ramped up its threats against Anthropic, other Silicon Valley workers saw how the situation could apply to them. If Anthropic was cut off from government business for not capitulating to the Pentagon’s demands, the same tactics could be used on them.

Some employees at large AI companies soon signed proposals calling on managers to support Anthropic’s position. On chats and messaging boards, engineers said that if the Pentagon carried out its threat, nothing was stopping it from using the same tactics to force other companies to work with it.