A police horse was punched by a football fan amid clashes between rival supporters at the Portsmouth v Southampton derby.
Police said five men were arrested, with one, aged 52, being held in police custody on suspicion of animal cruelty.
Social media footage appears to show a series of scuffles between fans and police before and after the match.
One video shows a man striking the horse before being chased down the street by its mounted officer.
Other officers, who were then alerted, grabbed the suspect as he tried to escape, striking him with their batons before detaining him.
Hampshire Constabulary said the horse, named Luna, was uninjured and remained on duty.
The man arrested on suspicion of animal cruelty – which police said was related to a horse – was also arrested for attempted criminal damage.
The other four arrested included a 40-year-old man who was held on suspicion of possession of a pyrotechnic.
Two men aged 18 and 19 were given conditional cautions for a public order offence.
A 20-year-old arrested on suspicion of a public order offence was later released with no further action to be taken.
Hampshire Constabulary said policing the game at Fratton Park on Tuesday, which Southampton won 4-0, was the county’s largest football policing operation.
Assistant Chief Constable Scott Chilton said: “Sadly we had to prepare for the potential that a minority would try and ruin it for everyone else and this required us, in conjunction with both clubs and our partners, to put plans in place to ensure we were ready to stop that.
“The fact that we have had no reports of anyone being injured and only a few people arrested is testament to the hard work that everyone has put into this operation.
“Today everyone is talking about what happened on the pitch, not off it, which is exactly what we wanted.”
It was the first south coast derby in seven years and Saints’ first win on Pompey’s home turf since 1984.
Hundreds of officers were drafted in to head off any trouble during the derby clash.
Police were also given powers to stop and search fans or ask them to leave three areas – Southampton, Portsmouth and part of Fareham – until the early hours of Wednesday.
Multiple police riot vans, mounted officers, helicopters and dog units were used as measures at the game.
Tactics for the match also included police escorting those arriving by coach and train to and from the stadium to try to prevent rival fans meeting.
Southampton fans were held back at the stadium for 30 minutes after the final whistle.
The Premier League side eased to victory against their League One rivals to reach the last 16.