Unit XY-75847

From Memory Alpha, the free Star Trek reference

Unit XY-75847 was a group of Starfleet vessels patrolling near the Klingon Empire-Federation border in 2267.

Shortly after the declaration of war, Unit XY-75847 provided advance warning that the Klingons were en route to Organia, but was unable to supply details as to their strength.

The warning induced Captain Kirk to give Lieutenant Sulu specific orders regarding confrontation with the Klingons: "do not fight -- run, and return with the fleet." (TOS: "Errand of Mercy")