Amid increased international speculation that Moscow is poised to launch an assault on Ukraine, Russia on Thursday teamed up with Belarus for a series of combat air patrol flights aimed at sending a message that one U.S. defense official termed “pure bombast.”

The patrol flights consisted of Su-30SM fighters jets from Belarus and Russia, and were meant to prevent “violation of the border in the airspace” of Belarus by Ukraine and NATO, the Belarusian Defense Ministry announced Nov. 25 on Telegram.

Officials in Moscow confirmed via the state news agency, Tass, that the flights were meant to deter incursions into Belarus.