U.S. President Donald Trump's Golden Dome missile defense concept revives a controversial, decades-old initiative whose ambitious construction could upend norms in outer space and reshape relations between the world's top space powers.

Trump announced a plan to build a missile defense system, called the Golden Dome, on May 20, 2025.

The Pentagon has warned for years that the newest missiles developed by China and Russia are so advanced that updated countermeasures are necessary.