By Gabriel Partos
Central Europe analyst, BBC News
Hopes for unity around the flag have been washed away
This should have been a day of unity and celebration for all Hungarians.
The 1956 revolution is a public holiday and it is regarded by most people in Hungary as the finest moment of their history in the 20th Century.
For more than two years Hungary's government and a memorial committee have been working hard on staging an elaborate series of events to mark the 50th anniversary of the revolution.
Their hope was to remember the heroes and the victims.
But there was also an endeavour to give the world a display of national unity - of a nation that has come to terms with its past and is comfortable with its present as one of the most prosperous and stable of the former communist bloc countries.
Instead, Monday's commemorations have been marred by running street battles between hardcore opponents of the government and the police.
Meanwhile, the main opposition party, Fidesz, held its own mass rally and boycotted the official events.
The anti-government protests and occasional bouts of violence go back more than a month.
Hungary had spent two years working on the festivities
They were triggered by a leaked tape of Prime Minister Ferenc Gyurcsany admitting that his government had lied about the true state of the public finances before it was returned to office in April's general election.
An initial three nights of violence - involving, among others, known soccer hooligans - gave way to a peaceful encampment outside parliament of various extremists, including supporters of a greater Hungary and various racist groups.
Monday's violent demonstrations came after the breakdown of negotiations aimed at securing the departure of hardline demonstrators to make way for the official celebrations.
Police removed the protesters in the early hours - who later regrouped and attracted other supporters in the course of the day as they tried to march to the venues of key events during the revolution.
Battle over legacy
Behind these separate events marking the revolution there is a political struggle with a clear focus on gaining advantage for the present.
The small extremist groups are hoping to widen their support by appealing to the spirit of resistance that defined the revolution.
They have been using the symbols of 1956 - even though Hungary's present-day democracy has nothing in common with the communist dictatorship of 50 years ago.
For the mainstream opposition the legacy of the revolution remains a strong weapon against the government because the governing Socialists are the legal successors to Hungary's former communist rulers.
But they have a way of dealing with that by portraying themselves as the political successors to Prime Minister Imre Nagy, the communist reformer who led Hungary during the revolution - and paid for his principles by being executed under the Soviet-installed regime.
Ironically, there is a broad consensus among Hungary's historians about 1956 and the remarkable sense of national unity it produced, and history textbooks present a very balanced account.
But politicians and political activists have yet to be persuaded that anything other than their side's narrow interpretation has validity.