Microsoft Mobilizes Legal and Corporate Resources to Back Anthropic in Battle That Could Define AI’s Future Role in Defense

Microsoft has mobilized its considerable legal and corporate resources to back Anthropic in a legal battle that could define the future role of artificial intelligence in US national defense, filing an amicus 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 allowing the designation to stand would cause immediate harm to technology supply chains critical to national security. Amazon, Google, Apple, and OpenAI have also filed in support of Anthropic, making this a battle that the entire technology industry has a stake in winning.
The legal battle traces back to a $200 million contract negotiation in which Anthropic refused to allow its Claude AI to be used for mass surveillance of US citizens or to power autonomous lethal weapons. Defense Secretary Pete Hegseth labeled the company a supply-chain risk after negotiations collapsed, triggering the cancellation of Anthropic’s government contracts. Anthropic filed two simultaneous lawsuits in California and Washington DC, challenging the designation as unconstitutional and without precedent.
Microsoft’s mobilization of legal and corporate resources is grounded in its direct use of Anthropic’s technology in federal military systems and its partnership in the Pentagon’s $9 billion cloud computing contract. The company also holds additional agreements with government agencies spanning defense, intelligence, and civilian services. Microsoft publicly argued that the government and technology sector needed to work together to ensure advanced AI serves 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 expressed 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 ruled out any possibility of renewed negotiations.
Congressional Democrats have separately written to the Pentagon asking whether AI was involved in a strike in Iran that reportedly killed over 175 civilians at a school, raising fundamental questions about AI targeting and human oversight. Their formal inquiries are adding legislative urgency to a legal battle that may ultimately define the terms on which AI companies and the US military relate to each other for decades to come.