Officers responded to reports of an altercation in Robertson Street at around 12.30am on Saturday, November 20.
A 20-year-old man was taken to hospital for treatment for serious injuries.
Officers have released photographs of two men they believe may be able to help them with their enquiries.
A spokesperson for Sussex Police said: “If you recognise them, or have any other information about what happened, please report it online or call 101 quoting serial 39 of 20/11. Alternatively, you can contact the independent charity Crimestoppers anonymously on 0800 555 111.”