• On March 3, 2026, Defense Secretary Pete Hegseth designated Anthropic a supply-chain risk and ordered a six-month Pentagon phase-out after a dispute over military-use guardrails.
  • RunSafe Security CEO Joe Saunders told Reuters that certifying a replacement for an existing system on classified or military networks could take 12 to 18 months. That is an attributed estimate, not an enterprise migration average.
  • Anthropic says the designation reaches Claude use directly under Department of War contracts; Microsoft, Google and AWS said non-defense customers could continue using Claude.

The phase-out order and the certification estimate are different clocks

Reuters reporting published by Military Times on March 19 says Hegseth designated Anthropic a supply-chain risk on March 3 and ordered the Pentagon and its contractors to remove Claude after a six-month phase-out. The dispute concerned guardrails for military use. The six-month period is a policy deadline for the Pentagon; it is not the source of the 12–18 month number.

Saunders said that, when an existing system is replaced, certification of the alternative for classified or military networks could take 12 to 18 months. He presented that as an estimate of a security and accreditation process. Reuters did not measure ordinary enterprise migrations, and Anthropic did not announce a general Claude shutdown date.

Embedded military workflows explain the implementation risk

Reuters reported that Anthropic had announced a $200 million defense contract in July 2025 and that Claude became embedded in Pentagon workflows. The report said it was the first AI model approved to operate on classified military networks. Replacement therefore involves more than changing an API endpoint: affected programs may need to identify prompts, agents, data paths, access controls, test evidence and accreditation packages tied to the existing model.

The extent of that dependence remains partly uncertain. Pentagon staff, former officials and contractors spoke anonymously about resistance and continued use. Two anonymous people familiar with Palantir’s Maven Smart Systems told Reuters that prompts and workflows had been built with Claude Code; one said Palantir would need to replace the model and rebuild parts of its software. Those are attributed source claims, not confirmation that every Maven component or defense contractor has the same dependency.

Commercial Claude use sits outside the narrow contract scope

In its February 27 statement and March 5 update, Anthropic argued that the designation applies only when Claude is used directly for Department of War contract work. It said individual and commercial access, and a contractor’s unrelated work, were unaffected. That is Anthropic’s attributed legal interpretation, not a court finding.

TechCrunch reported on March 6 that Microsoft and Google would keep Claude available to customers outside the Department of War and that AWS customers and partners could continue non-defense workloads. Microsoft subsequently described Microsoft 365 Copilot as model-diverse, with Anthropic and OpenAI models available in its commercial product. These statements rebut a market-wide deadline; they do not guarantee that every product, region or contract will remain unchanged.

The legal dispute remains unresolved

The Associated Press later reported Anthropic’s legal challenge to the designation and broader federal restrictions. Anthropic alleges that the measures are unlawful; the government has defended the national-security rationale. The cited record establishes litigation, not a court ruling that has cancelled or upheld the designation.

What to watch

The operational questions are narrower than generic vendor lock-in: which Pentagon systems are covered, how the six-month instruction is implemented, which replacements obtain authorization, whether Palantir or other named programs confirm rebuild scope, and whether a court changes the order. Until those facts are public, the 12–18 month figure remains a named expert’s certification estimate for classified or military systems—not a migration forecast for ordinary enterprises.