A man was attacked as he stood outside a Sowerby Bridge nightclub.
The assault, in which a 42-year-old man from Halifax was injured, took place opposite the Roxy Bingo and Social Club on Wharf Street between 1am and 1.20am on Saturday, November 29.
It took place following a dispute inside and then outside the nightclub, and the attacker is believed to have run across the road before reportedly carrying out the assault.
Police are appealing for any witnesses to the assault, which happened just out of view of CCTV, to come forward. They are particularly keen to speak to four men captured on CCTV who appear to have witnessed the incident.
PC 1691 Clay of the Neighbourhood Investigation Unit, said: “We are investigating this incident and are particularly keen to speak to four men who are shown on CCTV as being outside the club at the time the reported assault took place and may well have witnessed what occurred.
“I am very keen to speak to these four men as witnesses and would ask them to contact myself at the Calderdale Neighbourhood Investigations unit on 101.
“Information can also be passed anonymously to CrimeStoppers in 0800 555111.”