Blessed John Paul II loved the Christmas season. Guests in the papal apartment during his pontificate found the seasonal decorations up early in Advent; and, following Polish custom, they stayed up until Feb. 2, the feast of the Presentation of the Lord. The Christmas meal was traditionally Polish. Every year, John Paul would call his lay friends in Cracow, all assembled in one apartment, and they would sing Polish carols together for hours, over the phone.

Thirty years ago, however, the season took on a more somber tone. For on the night of Dec. 12-13, 1981, the Polish state, through the Polish army, invaded Polish society and imposed martial law throughout the country. There was no provision for martial law in Poland's communist legal code, so what the Jaruzelski regime declared was, technically, a "state of war." It was a fitting phrase, if unintentionally ironic.

On Christmas Eve, John Paul II placed a lighted candle in the window of the papal apartment, a gesture of solidarity with an international initiative begun in Switzerland by two clergyman, to protest the communist attempt to crush the Solidarity movement. The papal World Day of Peace Message for Jan. 1, 1982, condemned "the false peace of totalitarian regimes" and at the Angelus that day, the Pope asked everyone to pray for Poland, for what was at stake there was of great importance, "not only for a single country, but for the history of man."

With the benefit of 30 years of hindsight, it now seems clear that the imposition of martial law in Poland in December 1981 was not an act of strength but one of weakness, by a regime so incapable of commanding the allegiance of those in whose name it claimed to rule that it could only compel obedience by violence. It took some time for this to become clear in Poland, a country frequently burdened by crushed hopes; John Paul's second pastoral pilgrimage to his homeland, in June 1983, did a lot to raise the spirits of his countrymen -- who rallied their energies such that, by 1987, the Pope could spend his third pilgrimage home laying the cultural and moral foundations for a post-communist Poland, which was born two years later in the Revolution of 1989.

Two days after the imposition of the "state of war," President Ronald Reagan hosted a lunch at the White House for the Vatican secretary of state, Cardinal Agostino Casaroli. As I report in ''The End and the Beginning,'' it was Cardinal Casaroli who, over the course of a 90-minute discussion, took the Realpolitik view: however unfortunate martial law might be, there were likely reasons of state that compelled General Wojciech Jaruzelski, concerned about a possible Soviet invasion to crush Solidarity beneath Red Army tank treads, to behave as he did. And it was Ronald Reagan who, speaking in the tones of John Paul II, was the voice of moral outrage over this latest usurpation of Polish liberties. As the historical record now makes clear, John Paul and Reagan had it right, and the veteran Vatican diplomat had it wrong: there was no invasion threat in December 1981 (although there had been one in December 1980); the Jaruzelski regime was a hollow, if brutal, shell; the power of moral conviction, aroused, could be an effective antidote to communist tyranny, forging hitherto unimagined and effective tools of resistance; there was nothing permanent about the post-Yalta division of Europe.

The lessons, 30 years later? Solidarity's triumph ought not be universalized as a one-size-fits-all model for coping with tyrants. Still, John Paul II's instinct for reading history through cultural lenses has much to commend it. Politics and economics are important. What drives history over the long haul, however, is culture: what men and women cherish, honor, and worship; what men and women are willing to stake their lives, and their children's lives, on.

The truest realism, therefore, is one shaped by truths and ideals, not only by calculations of power. If you doubt that, ask General Jaruzelski.

George Weigel is Distinguished Senior Fellow of the Ethics and Public Policy Center in Washington, D.C.