By Jan Repa
BBC Europe analyst
Sunday 14 August 1980 was a turning-point in Polish history: the day the Gdansk shipyard strike started, paving the way for Solidarity.
Solidarity brought books and libraries to the Polish shipyards
It was the first independent mass political movement to emerge in the Soviet bloc.
But the debate continues over Solidarity's significance for the ultimate collapse of East European communism.
On 31 August 1980, Polish government representatives signed an agreement with striking shipyard workers, authorising the establishment of a new trade union free of communist control.
Sixteen months later, the experiment in political co-existence came to an end, with tanks on the streets and mass arrests.
Re-legalised in 1989, Solidarity soon took over Poland's government from the communists - but then rapidly disintegrated amid acrimony and mutual recriminations.
Stalin once said that establishing Communism in Poland was like trying to saddle a cow. The largest of Moscow's post-World War II satellites, Poland had a long history of conflict with Russia, and a tradition of personal freedom, Roman law, and limited government, very different from Russia's.
For three decades, it rumbled away like an indigestible meal inside the Soviet stomach. Stalin's terror gave way to a more flexible form of dictatorship.
By the 1970s, many young Poles were travelling to the West to see relatives and to moonlight, their awareness of living in an impoverished backwater becoming more acute.
Then, in 1978, a Polish archbishop, Karol Wojtyla, was elected Pope - taking the name John Paul II. His return visit to Poland the following year turned into a triumphal progress, with millions turning out to greet him.
Gdansk shipyard worker and future Solidarity leader, Lech Walesa, summed up the effect: "The Holy Father, through his meetings, demonstrated how numerous we were. He told us not to be afraid".
On 31 August 1980, the communist authorities conceded the strikers' main demand: their own trade union, independent of communist control. Soon Solidarity was claiming 10 million members.
In Lech Walesa, it also found its "People's Tribune". With his rough and ready manners, mangled grammar, ostentatious Catholic piety and apparent lack of humbug, he was "Our Lech".
Solidarity blatantly contradicted the Soviet principle that every aspect of public life had to be animated and controlled by the Communist Party. It soon evolved into a mass movement for civil and national rights - but of a peculiar kind.
Its intellectual advisers coined the term "self-limiting revolution". Society, they said, would organise itself from below - but would not make a direct grab for power.
The communist regime - hollowed out from inside - would remain as a facade, protecting Poland from Soviet attack.
One of the first elements of the communist system to disintegrate was censorship - as a Solidarity activist later explained to the BBC.
Pope John Paul II played a major role, inspiring many Poles
"We were setting up libraries of independent publishing inside the enterprises," he said. "I have the impression that many workers were only then starting to read books."
But if Solidarity promoted personal and social freedom, the West was not necessarily seen as a model. Solidarity saw itself as driving a moral revolution: an end to the mutual suspicion, self-abasement, double-talk, influence-peddling and corruption of life under communism.
Meanwhile, the Czech and East German authorities successfully exploited traditional anti-Polish prejudices. And as developments in 1981 would amply demonstrate, two of the Polish regime's institutions remained relatively untouched: the army and the secret police.
Years later, Prime Minister Wojciech Jaruzelski sought to justify martial law as the lesser of two evils:
"This was our own sovereign decision - but one which took into account the realities of those times. At that time the socialist system was the reality of that state - its backbone. And toppling that reality would have meant both civil war and foreign intervention."
The Soviet invasion threat has never been proved. Former members of the Soviet leadership have said that armed intervention was discussed - but rejected.
Mr Jaruzelski certainly did Moscow a favour, by sparing it the international opprobrium which would have followed an invasion.
But martial law did play into the hands of right-wing US President Ronald Reagan, who used the Polish crisis to step up Washington's ideological confrontation with the Soviet Union.
Wojciech Jaruzelski could not stem the tide of opposition
Behind the trappings of a military junta, the Polish leadership tried to reassemble the familiar structures of a communist regime. But the old fear had gone.
Confrontations between demonstrators and the Zomo riot police went on for months. Eventually, the regime, society and the Solidarity underground settled down to a sullen co-existence.
A new reforming Soviet leader, Mikhail Gorbachev, paid a visit - but appeared badly out of touch. If Poles wanted their own reformer, he reportedly told a roomful of silent communist activists, they had one in Jaruzelski.
When in 1988 UK Prime Minister Margaret Thatcher arrived in Gdansk, she was greeted with chants of "Send the Reds to Siberia!"
Later that year, the Jaruzelski leadership authorised talks with what it dubbed the "responsible opposition". The result was Solidarity's re-legalisation and partly-free parliamentary elections in the summer of 1989.
To its own surprise, Solidarity won all but one of the seats it had been allowed to contest. On 25 August, Tadeusz Mazowiecki, a veteran Catholic newspaper editor and Solidarity adviser, was sworn in as prime minister.
But Solidarity's victory proved an anti-climax - being quickly overshadowed by events elsewhere in Central and Eastern Europe.
In November 1989 the Berlin Wall came down.
That same month, Prague experienced its own "festival of freedom", when half a million people flocked to Wenceslas Square to hear the future Czech President, Vaclav Havel, denounce the communist regime.
In December, Romania's dictator Nicolae Ceausescu was deposed and shot. Suddenly, Poland's "negotiated transition" looked rather timid.
Prime Minister Mazowiecki announced he was "drawing a thick line" over the past: thus apparently precluding any serious investigation of communist crimes.
Lech Walesa: 1980s hero still hoping for a comeback
But it was the younger Communist Party reformers who proved to be quicker on their feet.
In 1990, the Polish Communist Party abandoned Marxism-Leninism, renamed itself the Democratic Left Alliance and redefined itself as a "social-democrat party of the West European type".
In 1993, it won the parliamentary elections and in 1995, its leader Aleksander Kwasniewski defeated Lech Walesa in presidential elections.
Mr Kwasniewski had been a junior minister in the last communist government of the 1980s. In retrospect, he is highly critical of Mr Jaruzelski's decision to impose martial law in 1981, not least because of its longer-term psychological effects:
"We will never know whether - to use the colloquial expression - the 'Ruskis' would have come in and when. Martial law was an evil. Evil, because it was directed against our reviving freedom. Evil, because it quenched revived hopes for a life lived in dignity, for civil liberties and democracy."
Perhaps the summer of 1980 represented a unique moment: when economic crisis, working class discontent, intellectual ferment, a tired and clueless regime, and an upsurge of national pride in the new Pope, combined to produce a dynamic chemical reaction.
However, sectional interests, class prejudices and personal ambitions quickly reasserted themselves.
There have been huge changes in Poland since the fall of communism. Newsreel footage of the Gdansk strikers - moustaches, bad haircuts, polyester trousers and all - show a vanished era, as remote to many younger Poles as top hats and walking sticks.
Lech Walesa still dreams of a political comeback. General Jaruzelski concentrates on his memoirs and on avoiding jail.
Most significantly perhaps, Poles have discovered an unexpected talent for hard work and wealth creation.
But the country's booming "enterprise culture" appears to have little obvious connection with Solidarity's old communitarian ethos - except as an expression of an underlying desire for freedom.