Microsoft has backed Anthropic in a legal fight that will ultimately determine whether AI companies have the right and the power to stand up to the US military over how their technology is used, filing a court brief in a San Francisco federal court calling for a temporary restraining order against the Pentagon’s supply-chain risk designation. The brief argued that the designation threatens the technology supply chains supporting national defense. Amazon, Google, Apple, and OpenAI have also backed Anthropic in this defining confrontation.
The fight began when Anthropic refused to allow its Claude AI to be used for mass surveillance of US citizens or autonomous lethal weapons during a $200 million Pentagon contract negotiation. Defense Secretary Pete Hegseth labeled the company a supply-chain risk after talks collapsed, and the Pentagon’s technology chief publicly ruled out any renegotiation. Anthropic filed two simultaneous lawsuits in California and Washington DC challenging the designation.
Microsoft’s backing in this defining fight is grounded in its direct integration of Anthropic’s technology into military systems and its participation in the Pentagon’s $9 billion cloud computing contract. Additional agreements with defense, intelligence, and civilian agencies give Microsoft a significant stake in the outcome. Microsoft publicly argued that the government and technology sector needed to cooperate to ensure advanced AI served national security responsibly.
Anthropic’s court filings argued that the supply-chain risk designation was an unconstitutional act of retaliation for the company’s publicly stated AI safety positions. The company disclosed that it does not currently believe Claude is safe or reliable enough for lethal autonomous operations, which it said was the genuine basis for its contract demands. The Pentagon’s technology chief publicly foreclosed any possibility of renegotiation.
Congressional Democrats have separately pressed the Pentagon for answers about whether AI was used in a strike in Iran that reportedly killed over 175 civilians at a school, adding legislative urgency to the confrontation. Their inquiries underscore the broader stakes of a fight that will determine whether AI companies can effectively stand up to the US military on questions of AI ethics. Microsoft’s backing of Anthropic may prove to be one of the most consequential corporate decisions in the history of the AI industry.