Three men have been arrested after a police officer was punched and stamped on and her colleague was left unconscious.
The officers were on their way to another incident, when they tried to stop the brawl in Middleton, Greater Manchester, on Saturday.
The female officer was dragged to the ground and her male colleague was knocked out with a punch to the head.
Three men have been held on suspicion of violent disorder.
Two of the men, aged 29 and 34, have also been held on suspicion of attempted assault.
Both officers were treated in hospital and are now recovering at home, Greater Manchester Police said.
On Saturday, Det Sgt Tim O'Callaghan said: "This is a disgusting way to treat police officers, who spend their days and nights trying to keep the people of Greater Manchester safe.
"We will not tolerate this kind of behaviour and are 100% committed to bringing those responsible to justice."
The attack happened after "Mad Friday" - the last Friday before Christmas, which sees a spike in alcohol-related incidents, and has become one of the busiest days for the emergency services.