Microsoft’s Legal Push for Anthropic Marks a Turning Point in the AI Industry’s Relationship With the US Military

Microsoft’s decision to file a court brief supporting Anthropic in its battle against the Pentagon marks what many observers are calling a turning point in the relationship between the AI industry and the US military. The brief was filed in a San Francisco federal court and called for a temporary restraining order against the Pentagon’s unprecedented supply-chain risk designation. The filing joined a wave of industry support that includes Amazon, Google, Apple, and OpenAI, all of whom have backed Anthropic through their own court submissions.
The dispute began when Anthropic refused to enter a $200 million contract to deploy its AI on classified military systems without protections against its use for mass surveillance or autonomous weapons. Defense Secretary Pete Hegseth responded to the collapse of negotiations by labeling the company a supply-chain risk, a designation with severe and immediate consequences. Anthropic filed two simultaneous lawsuits, one in California and one in Washington DC, arguing the designation was unconstitutional and without precedent.
Microsoft’s brief is informed by its own use of Anthropic’s AI in federal military systems and its status as a partner in the Pentagon’s $9 billion Joint Warfighting Cloud Capability contract. The company also holds additional multibillion-dollar agreements with various government agencies, making it one of the most deeply embedded tech partners in the federal government. Microsoft’s public statement called for a path forward that allows the government to access the best AI technology while ensuring that technology is not misused for surveillance or unauthorized warfare.
In its court filings, Anthropic argued that the supply-chain risk label was being wielded as a political weapon against a company that had publicly advocated for responsible AI development. The company stated that it does not currently believe Claude is safe or reliable enough for lethal autonomous operations, which it said was the legitimate basis for the restrictions it sought. Anthropic’s legal team noted that the designation had never before been applied to a US company.
Congressional Democrats have formally asked the Pentagon whether AI was used in a strike in Iran that reportedly killed over 175 civilians at an elementary school, and whether human review processes were followed. These inquiries are running parallel to the legal battle and adding legislative pressure to the Pentagon’s position. Together, they represent a historic convergence of legal, legislative, and corporate pressure that is forcing the US government to publicly defend its approach to AI in warfare.