Theseus, a defense technology startup based in San Francisco, has raised $4.3 million in seed funding to develop GPS-free military drones. The company has created a Micro Visual Positioning System that serves as an unjammable alternative to GPS, enabling U.S. Special Forces to conduct missions that were previously not possible. The funding round was influenced by a viral tweet that caught the attention of Y Combinator and the U.S. Special Forces. Theseus is part of a broader trend of hard tech startups gaining traction and raising larger funding rounds due to demonstrated technological breakthroughs and commercial validation. The company was supported by investors including Y Combinator and received a $500,000 investment following a chance meeting with CEO Carl Schoeller. Theseus aims to enhance defense capabilities by providing reliable positioning systems for military drones, addressing vulnerabilities associated with GPS reliance.