On August 31, 2026, the US Defense Department began offering OpenAI's ChatGPT Mil on GenAI.mil, its internal generative AI platform. Starshield AI's Grok for Government arrived the same day, joining Google's Gemini so that users can pick among several frontier models. The scope is everyday work involving unclassified but protected information, with more than 3 million people in the intended user base.

Cleared for information that is sensitive but not classified

ChatGPT Mil covers CUI (Controlled Unclassified Information) — government information that carries no classification marking yet still requires specific safeguards. The department says ChatGPT Mil is accredited to handle that material at Impact Level 5 (IL5), the tier in the department's cloud security scale that permits sensitive unclassified data.

At launch the experience includes chat, files, projects and custom GPTs, with more features expected over time. The work it targets is document-heavy: planning, policy, logistics and administration. OpenAI points to disaster-response planning, resource allocation, reconciling supply and maintenance records, and drafting transportation requirements as concrete examples.

On data handling, anything processed on GenAI.mil stays isolated inside the government environment and is not used to train or improve public or commercial models. Navy guidance permits CUI but forbids entering personally identifiable information or protected health information.

1.7 million users in nine months, and no single vendor

GenAI.mil went live in December 2025, and the department says unique users have already passed 1.7 million. With more than 3 million personnel across the department, that is a little over half of the workforce in nine months.

For the Navy and Marine Corps it is already an enterprise requirement. A January 2026 memorandum designated GenAI.mil as the Department of the Navy's mandated CUI and IL5 generative AI platform and directed commands and organizations to move to it by April 30.

Adding Grok for Government on the same day is worth noting. The department framed the move as a way to avoid vendor lock-in and widen the domestic AI ecosystem. Officials describe Gemini as the better fit for search-style use and ChatGPT as the better fit for text-centered work, so users choose a model per task. Not betting the whole department on one model has become the platform's design principle.

An operations order finished in six weeks

The department's headline example comes from the Army's XVIII Airborne Corps. According to congressional testimony in May 2026, the corps used GenAI.mil to produce a complete exercise operations order covering the US Southern Command area of responsibility in six weeks. Work that traditionally took a much larger staff six to nine months was handled by nine writers.

What mattered was less raw drafting speed than the compression of the draft-and-review cycle. Military documents carry fine-grained formatting and cross-references, and simply conforming to the template eats hours. Hand that to a machine and people can spend their time on judgment instead.

Deliberately separate from combat use

The boundary is explicit. GenAI.mil is an IL5 platform for unclassified work, distinct from the classified-network AI the department is developing and testing separately for warfighting. Both the department and OpenAI say there is no intent to use models on GenAI.mil for combat.

Getting a frontier model onto GenAI.mil also requires security testing involving the Defense Information Systems Agency and the National Security Agency. Commercial models cannot simply be dropped in; a review sits in the way. Joe Larson, who leads government sales at OpenAI, says the aim is to make unclassified work more efficient while preserving safeguards, human judgment and accountability for high-stakes decisions.

Summary

The US Defense Department added ChatGPT Mil and Grok for Government to GenAI.mil on the same day, extending it into a platform where Gemini is one option among several. Accredited for CUI at IL5, it targets document-centered work in planning, policy, logistics and administration. Users passed 1.7 million in nine months, and the Navy has made the move mandatory. Kept apart from combat use, generative AI is taking root in the military through unglamorous paperwork first.

※The thumbnail image is AI-generated.