Microsoft has publicly supported Anthropic in its legal battle against the U.S. Pentagon, arguing that the military department's decision to blacklist the AI company endangers the broader technology sector and American business. In a legal filing submitted on Tuesday, Microsoft warned that the Pentagon's effective ban on Anthropic poses negative ramifications for the entire industry. The company stated that this action risks the very AI ecosystem that the current administration has worked to promote. The conflict stems from a recent determination by Defense Secretary Pete Hegseth, who labeled Anthropic and its products as a supply chain risk. Consequently, the Pentagon has ordered defense contractors to cease doing business with Anthropic immediately. Additionally, President Donald Trump has directed federal agencies to phase out their use of Anthropic's models within six months. However, Microsoft highlighted a significant disparity in these rules: while the Department of Defense was granted a six-month window to transition away from Anthropic's services, private contractors face an immediate cutoff with no transition period. Microsoft emphasized its vested interest in the outcome of the case, having pledged up to $5 billion to Anthropic in November as part of a major partnership involving Nvidia. The tech giant argued that implementing this designation immediately imposes substantial costs and risks on Microsoft and other government contractors who rely on Anthropic's technology as a foundational layer for their own products and military services. During Monday's court proceedings, Anthropic sued Hegseth, the Pentagon, and various federal agencies to block the order temporarily and prevent its permanent implementation. Microsoft joined this effort through a proposed amicus brief, echoing concerns raised by Anthropic CEO Dario Amodei regarding AI safety. Microsoft's legal team argued that artificial intelligence should be restricted to lawful and properly guarded use cases. They specifically warned against the deployment of AI for domestic mass surveillance or the initiation of autonomous warfare without human oversight. This legal dispute has garnered significant attention from the Silicon Valley community. OpenAI CEO Sam Altman had previously urged the Pentagon to reconsider the supply chain designation, while dozens of employees from OpenAI and Google, including Google's chief scientist Jeff Dean, signed a separate brief opposing the Pentagon's actions. Despite these concerns, Pentagon officials and Defense Secretary Hegseth have rejected arguments that the current order ignores the risks of autonomous weapons or domestic spying. A Microsoft spokesperson noted that all parties require time and a structured process to reach a consensus. The spokesperson emphasized that the Department of Defense needs reliable access to the country's most advanced technology while ensuring that AI is not misused to start wars without human control or conduct mass surveillance. Microsoft asserted that the government, the technology sector, and the public must find a collaborative path to achieve these shared goals.