A woman police officer was beaten unconscious after responding to reports of a disturbance in Sussex.
The officer was sent to the incident in Riley Road, Brighton, as a back-up on Wednesday evening.
She was the first to arrive on the scene where she was attacked, said Sussex Police.
"She was knocked to the ground and kicked and punched in the head. She was unconscious for a time," said Ch Insp Helen West.
She was helped at the scene by other police officers and members of the public before being taken to the Royal Sussex hospital for treatment.
A youth was later arrested.