WASHINGTON (AP) — Meta CEO Mark Zuckerberg took the stand Monday in a historic antitrust trial that could force the tech giant to break off Instagram and WhatsApp, startups it bought more than a decade ago that have since grown into social media powerhouses.

The Federal Trade Commission called Zuckerberg as its first witness, as it seeks to prove that Meta acquired Instagram and WhatsApp to preserve its monopoly in the social networking space.

In opening statements, FTC attorney Daniel Matheson said Meta has used its position to generate enormous profits even as consumer satisfaction has dropped. He said Meta was “erecting a moat” to protect its interests by buying the two startups because the company feared they were a threat to Meta’s dominance.

Zuckerberg and other key Meta witnesses will testify throughout the trial.

“We’re going to give them their chance to tell their side of the story,” Matheson said.