Thirty police officers swooped on Wallingford town centre after more than 50 youths started a drunken brawl.
A member of the public raised the alarm at 10.36pm on Friday after seeing 30 men fighting in High Street.
But by the time police officers arrived, there were about 50 youths fighting in High Street and the market square.
Victoria Bartlett, a spokeswoman for Thames Valley Police, said yesterday that more than 30 officers were called, including those manning the force helicopter. There were also dog handlers and roads policing officers involved.
Officers remained in the area for two hours, arresting 18 youths - 15 males and three females.
Julian Walley, a local estate agent, who took pictures of the police operation with his mobile phone camera, said the area was flooded with police.
He said: "Police cars pulled in from various areas around town into the centre.
"There was a police helicopter, police with dogs, patrol cars, riot vans and a police tow-truck - I have never seen anything like it.
"Wallingford is usually a lovely quiet market town. It has only got a population of about 7,000 and this is just not what you expect.
"The police responded with a lot of manpower - this wasn't an ordinary fight."
A Thames Valley Police spokesman said the brawl began on High Street and spilled into the market square.
Ronnie Jones, also from Wallingford, said: "We saw the police cars drive past the pub - there was seven of them and then two police vans followed.
"Then we heard the police helicopter - it made quite a racket. Wallingford is normally quite a quiet place."
Joanna Carrington, landlady of The Town Arms pub, next to Wallingford Bridge, said a group of youths gathered near the pub before walking over the bridge back into the town centre.
She added: "Some of these kids must have been as young as 14. They had too much to drink and then they started arguing. But the trouble did not start in any of the pubs."
Following the incident, a 39-year-old woman was cautioned for assault, and a 15-year-old boy was released on police bail pending further enquiries.
A further 15 were dealt with by fixed penalty tickets for public order offences. A 17-year-old boy has been charged with assault and resisting arrest and will appear at Didcot youth court on September 29.
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