Battle stations

General quarters, battle stations, or action stations is an announcement made aboard a naval warship to signal that all hands (everyone available) aboard a ship must go to battle stations as quickly as possible.

According to The Encyclopedia of War, formerly "[i]n naval service, the phrase "beat to quarters" indicated a particular kind of drum roll that ordered sailors to their posts for a fight where some would load and prepare to fire the ship's guns and others would arm with muskets and ascend the rigging as sharpshooters in preparation for combat."

...
Wikipedia