Microsoft Warns Pentagon Move Against Anthropic Could Disrupt Military Systems

Microsoft has intervened to support Anthropic in its legal battle with the US Department of Defense, warning that the Pentagon’s decision to blacklist the artificial intelligence company risks disrupting critical military technology systems.

In a filing submitted on March 10 to the US District Court for the Northern District of California, Microsoft asked the judge to issue a temporary restraining order preventing the Pentagon from enforcing its designation of Anthropic as a “supply chain risk” for existing contracts.

The company argued that such an order would allow time for an orderly transition and avoid sudden disruption to the military’s use of advanced AI systems.

Without court intervention, Microsoft said contractors and technology providers working with the Pentagon would be forced to immediately reconfigure products and contractual arrangements that currently depend on Anthropic’s technology.

The company warned that the consequences could be significant for operational systems used by the US military. In its submission, Microsoft said the abrupt changes could “potentially hamper US warfighters at a critical point in time”.

The legal dispute follows a decision by the Department of Defense last week to ban Anthropic’s technology and label the company a supply chain risk, a designation historically reserved for firms associated with foreign adversaries.

Under the classification, defence contractors must certify that Anthropic’s AI models are not used in projects linked to the Pentagon.

Anthropic responded by filing a lawsuit against the administration of US President Donald Trump on March 9, arguing that the government’s actions were “unprecedented and unlawful”. The company said the move threatened hundreds of millions of dollars in contracts and could cause significant financial harm.

Microsoft’s intervention came through a proposed amicus brief, a legal submission made by a party not directly involved in the case but with a stake in its outcome.

The software company has a significant financial interest in Anthropic. In November, Microsoft announced plans to invest up to $5 billion in the company, even as it remains the largest backer of OpenAI, a partnership dating back to 2019.

In its filing, Microsoft said a temporary restraining order would provide both sides time to pursue a negotiated settlement while preventing disruption to government technology systems.

“We believe everyone involved shares common goals, and we need time and a process to find common ground,” a Microsoft spokesperson said. “The Department of War needs reliable access to the country’s best technology. And everyone wants to ensure AI is not used for mass domestic surveillance or to start a war without human control.”