Only a heavy police presence prevented violent clashes at a Republican parade in Glasgow, a senior officer has said.
Police said their presence prevented "serious disorder"
About 1,000 marchers took part in the Bloody Sunday commemoration as 400 protesters jeered and threw bottles at the procession.
Police said 11 people were arrested for offences including breach of the peace, assault and possession of a knife.
Strathclyde Police Assistant Chief Constable Kevin Smith said officers had managed to prevent "serious disorder".
Parade organiser Jim Slaven said he was happy the rights of the Irish community in Scotland had been upheld.
Trouble had flared at the same event last year, when marchers and protesters were involved in violent clashes in the city's George Square.
Many police officers kept the two sides apart in the same area on Saturday.
Mr Smith said there was racist and sectarian abuse at the event and that without the presence of so many officers the consequences would have been unimaginable.
"If we hadn't been there in the numbers in which we were there would have been serious, serious disorder on the streets of Glasgow," he said.
"We had to deploy a significant number of officers to ensure that a group of 300 or 400 did not attack a procession of 1,000 or more.
"You can only imagine what could have happened if that had occurred."
He said officers dealt with incidents such as missile throwing but said there were no reported injuries.
He added: "Many of those taking part in the procession clearly antagonised the protesters.
"Unfortunately, but not unexpectedly, racist and sectarian abuse was present."
The senior police officer also revealed the start of the parade was held up as some of those taking part were dressed in paramilitary-style clothing.
Protesters jeered and threw missiles at the marchers
He said: "Unfortunately the start of the march was delayed by almost 30 minutes as, contrary to permission conditions, there were groups dressed in paramilitary-style clothing.
"There were further problems with aspects of the organisation of the parade that we will now take forward with the organisers and Glasgow City Council."
Mr Smith added that officers would now begin studying CCTV footage from the march to see if there was evidence for more arrests.
Mr Slaven, organiser of the parade by Cairde na hEireann (Friends of Ireland), said he was happy marchers' rights had been protected.
"That's what we would expect. People on the parade behaved with great dignity and respect. It was a peaceful march from our point of view," he added.
BBC Scotland's Gillian Sharpe said the atmosphere in George Square during the parade was "tense".
She said the square was full of Unionist protesters who were waving placards and Union flags while shouting at the marchers.
Before the march, senior officers said troublemakers would be firmly dealt with, including anyone using offensive chants or expressing support for paramilitary organisations.
New legislation currently being drafted would give the police greater powers to block problem parades.