Anti-EU parties had their best results in the latest European Parliament elections.
By William Horsley
BBC European affairs correspondent
They aim to be the Trojan Horse that brings down the fortress of a federal Europe from inside.
The UK Independence Party raided political heartland of mainstream parties
They are now within the gates, though heavily outnumbered.
They comprise a mixed band of political warriors - the Eurosceptics, the nation-state sovereignists and the anti-corruption fighters.
They are about to claim their seats in the European Parliament, an institution which they deride.
Will it end in a rout, like in A Bridge Too Far?
Or in a triumph against the odds, as in The Guns of Navarone? The next five years will tell.
The Euro-critics have become famous in the past few days, thanks to media publicity and a strong message.
In London, there was dismay among the mainstream, Euro-critical Conservatives, as the UK Independence Party (UKIP) raided their political heartland.
UKIP demands Britain's outright withdrawal from the EU. It took 12 seats in the Strasbourg parliament, against 27 for the Conservatives.
Overall, the Euro-critics still face a solid block of MEPs who believe in the motto of the integrationists - an 'ever-closer union' for Europe.
In Poland, the Catholic, anti-EU League of Polish Families won second place among the parties and 10 seats.
Maciej Giertych, one of their leaders, says Poland must quit the EU to enjoy real independence.
His group is sworn to stop the birth of a "Federal Republic of Europe".
Another band of seven Poles from the Self-Defence of Poland party also oppose Poland's terms of EU accession and the "Brussels system".
Even in France, the leader of the French "Souverainistes", Philippe de Villiers, held on to three seats for his Movement for France, which rejects both the euro and France's EU membership.
Eurosceptics of various colours won small victories elsewhere, too.
In the Netherlands, Paul van Buitenen, the "whistle-blower" against EU corruption, won two seats for Transparent Europe.
In Austria, ex-journalist Hans Peter Martin won a surprise two seats for his personal list, after he exposed the expense-fiddling of MEPs (Members of the European Parliament).
And in Sweden, another new-born Eurosceptic group, the June Movement, captured 3 seats.
A Dane, Jens-Peter Bonde, leads the main Eurosceptic group in the parliament, called "Europe of Democracies and Diversities".
He expects his group to roughly double in size from just 18 to around 40.
Ahead lies the prospect of popular referendums in up to half the EU's 25 member-states, on the constitution and the future of Europe
That would include the Poles, Swedes, the de Villiers' group from France and UKIP.
They have more potential allies for their cause among other right-of-centre groups, including the British Conservatives and 9 Czech Civic Democrats, who are likely to sit, officially, with the integrationist Christian Democrats from Germany in the main centre-right grouping.
Loud anti-EU talk also comes from the political extremes, both the far-left communists and the far-right National Front of France, which has won eight seats.
More battles ahead
But overall, the Euro-critics still face a solid block of about two-thirds of MEPs in the 732-seat parliament, who believe in the motto of the integrationists - an "ever-closer union" for Europe.
The EU's political calendar now bristles with dates for the political battle to be engaged.
On 17 June, EU leaders will try once more to agree the text of a legally-binding EU constitution.
On 20 July, the new European Parliament meets for the first time.
Ahead lies the prospect of popular referendums in up to half the EU's 25 member-states, on the constitution and the future of Europe.
The outcome will decide the fate of nations, and of many of Europe's politicians on both sides of the great debate.