It seems like the opening of a techno-thriller novel or (spoiler alert!) a scene from the latest Gerard Butler movie: In the dead of night, a swarm of robotic planes sneaks past a billion-dollar defense system and then takes out one of the world’s most valuable targets in a fiery blast.

But it is no fiction. It is now a technological and political reality.

Much remains uncertain about the raid on oil facilities in Saudi Arabia on Saturday that shut down half the country’s oil output. Saudi officials initially credited the attack to “drones,” with Houthi rebels in Yemen then claiming responsibility. But soon there were disputes about the origin of the attack (some in the Trump administration have fingered Iran instead of Yemen) as well as the weapons used (experts are debating whether it was only armed drones — or a mix of drones and cruise missiles).

What we know for certain is that the attack points to crucial changes in the technology of war and its consequences that the United States should prepare for better than the Saudis did.

The most advanced weapons used to be found only in the hands of the most powerful state actors, because of how much it cost to obtain them and the expertise required to use them. Now there is a much lower barrier to entry. More than 75 nations have cruise missiles and more than two dozen nations have armed drones. Those numbers will continue to grow as more sellers like China introduce the technology into the world arms market. (As fate would have it, the Saudis recently bought Predator-drone knockoffs from Beijing.)