The former Polish President Lech Walesa has paid tribute to the independent trade union Solidarity which played a key role in the collapse of communism.
Lech Walesa: "No manipulation or treason" behind Solidarity
The strike by Solidarity members "changed the face of the Earth," Mr Walesa told the Polish parliament.
He was launching three days of celebrations on the 25th anniversary of Solidarity, founded by him and fellow shipyard workers in Gdansk.
Several European leaders are going to Poland for the celebrations.
They include the President of the European Commission, Jose Manuel Barroso, and the German President Horst Koehler.
The celebrations will culminate with a mass in Gdansk on Wednesday.
Mr Walesa, who spearheaded the Gdansk protests, said that in 1980, "arm-in-arm, workers and intellectuals and even, to some extent, recent opponents joined together in a march to freedom".
"For the first time in post-war times, all social groups met under the one banner of Solidarity...
"We bow today before our most recent history, as we want to nurture and continue carrying the message of Solidarity," Mr Walesa said.
He insisted that there was "no manipulation or treason" behind the scenes in Solidarity's actions.