Martin Smith, 45, was with his eight-year-old son in Seafield Park when he remonstrated with a group of 30 youths who were setting fire to aerosols.
The former RAF air traffic controller, who got involved to help a woman who was getting abuse from the group, said that as he started to film the incident two of the teenage boys turned on him.
He was forced to flee with his little lad who was screaming as his dad was hit.
Mr Smith told The News: ‘The atmosphere changed just like that – I heard rumblings around me.
‘One of them got emboldened by that and said “what you going to do about it?” I said “what I’m going to do is take my camera out and film it”.’
He added: ‘I heard a commotion and there was this lad, 6ft 1in, with a big 2ft stick, a big branch. He does this little weird spin round and knocked the phone off my hand.
‘Whilst I’m down getting the phone he’s taken a two-handed swing with the stick into my rib cage and cracked a couple of ribs.
‘He was trying to do it again. I stood up and disarmed him, took the stick out his hand and got him into a restraint position and held him there.
‘He was still trying to punch me, The bigger lad then started to punch me and kicked me in the face.
‘At that point my son was still screaming his head off. It was really scary.’
Mr Smith then pushed one teenager away and shouted for his son to run. But as he ran Mr Smith tripped over and the attacker tried to kick him in the head.
Mr Smith eventually got away and called 999 and four police cars attended.
The victim said the teenager who attacked him with the branch was brazen and stayed put even as police arrived to deal with the incident.
Mr Smith said his son has been left ‘traumatised’ but the neighbourhood went on a ‘reclaim walk’ over the weekend to enjoy the park and area to show they were not scared of doing so.
A Hampshire police spokesman said: ‘Police are investigating an assault which took place between 4pm and 4.30pm on Tuesday, April 11.
‘A 45-year-old man encountered a group of youths on Saltern Road, Stubbington.
‘It was reported that he was assaulted by two members of the group, and that a large stick was used during the assault. The victim sustained injuries to his face and body as a result.’
Call police on 101 quoting 44170135676.