On Monday, Russia issued an unusually cryptic threat, specifically to U.S. Air Force Chief of Staff Gen. David Goldfein on Twitter. The message cited the F-35, America’s most advanced stealth fighter, and included footage of Soviet-era surface-to-air missiles shooting down aircraft.

Just in case Russian officials decide to pull their tweet down at any point in the future, the written content reads:

‘If a Russia… ever was to see an F-35 inside its airspace’, we would love to send Chief of Staff of the @usairforce Gen. David L. Goldfein ‘message with two words’ — ‘remember Vietnam
‘An F-35 will never be alone’

While seemingly nonsensical, the tweet was actually a variation on General Goldfein’s own quotation. He made the following statement at the Brookings Institution on Tuesday:

If a China or a Russia or another adversary on the globe ever were to see an F-35 inside their airspace … I would love to send them all a message with two words: ‘We’re here.’ ”

“If they ever do see an F-35, which is highly unlikely, they will never be alone,” Goldfein added. “It will be part of a penetrating joint team.”