The Claude chatbot from Anthropic has taken the top spot among free apps in the US App Store, pushing OpenAI's ChatGPT to second place.

Source: App Store.

This shift in leadership is attributed to a mass exodus of ChatGPT users. Previously, OpenAI CEO Sam Altman announced a partnership with the US Department of Defense, agreeing to deploy its AI models within classified military networks.

Tonight, we reached an agreement with the Department of War to deploy our models in their classified network.

In all of our interactions, the DoW displayed a deep respect for safety and a desire to partner to achieve the best possible outcome.

AI safety and wide distribution of…

— Sam Altman (@sama) February 28, 2026

Anthropic CEO Dario Amodei publicly rejected such contracts, prohibiting the government from using the developer's AI for mass surveillance or creating autonomous weapons.

Former US President Donald Trump criticized Anthropic's decision, accusing the team of trying to dictate terms to the defense department. Following this, the Pentagon terminated contracts with the company and blacklisted it as a "national security threat." Shortly after, a military contract was awarded to OpenAI.

The company's decision sparked significant backlash within the community. A post on Reddit calling for a boycott of the chatbot garnered 30,000 likes, while the themed account quitGPT on Instagram attracted 78,000 followers.

Over 700 employees from Google and OpenAI also signed an open letter urging a halt to the use of AI in surveillance systems or for combat tasks without direct human oversight.

Outside Anthropic's office in SF… intense moment! pic.twitter.com/8uBPfZi0nc

— Roy E. Bahat (@roybahat) February 27, 2026

A representative from Anthropic told Mashable that since January, the number of free users of the service has increased by 60%, and the number of paid subscribers has doubled. Additionally, the daily rate of new registrations has tripled.

It is worth noting that in February, it was reported that SpaceX is involved in a Pentagon project to develop autonomous drones with voice control.