A teenage boy suffered a fractured jaw after he was assaulted at a park, police said.
The teenager was assaulted from behind as he was walking through St Nicholas Park, Warwick, with a friend at about 17:00 BST on 12 April.
Warwickshire Police said the suspect was understood to have shouted a boy's name before the attack, which was believed to have been a case of "mistaken identity".
Officers are appealing for any witnesses or those with mobile phone footage of the incident to come forward.
The suspect is described as white, about 13-years-old, approximately 5ft 6ins and wearing sunglasses and a dark-coloured tracksuit.
He was understood to have been with another teenage boy and both left in the direction of Warwick Railway Station, a force spokesperson added.
