The nightmare of nuclear war in Europe - a spectre that haunted the world for half a century - stood revealed yesterday in terrible detail. In a historic break with the past, Poland's newly elected government threw open its top secret Warsaw Pact military archives - including a 1979 map revealing the Soviet bloc's vision of a seven-day atomic holocaust between Nato and Warsaw Pact forces. The defence minister, Radek Sikorsky, showed off the map at an emotional press conference.

He described it as a "personally shattering experience", pointing to a long line of nuclear mushroom clouds neatly stamped along the Vistula, where Soviet bloc commanders assumed that Nato tactical nuclear weapons would rain down to block reinforcements arriving from Russia.

About two million Polish civilians would die in such a war, and the country would be all but wiped off the face of the Earth, he said. On the map, western Europe lay beneath a chilling overlay of large red mushroom clouds: Warsaw Pact nuclear strikes, using giant warheads to compensate for their relative lack of precision. Soviet bombs rain down on cities from northern Denmark down to Brussels, the political headquarters of Nato. Large red clouds blot out cities such as Hamburg, Frankfurt, Stuttgart, Munich and Baden Baden, Haarlem, Antwerp and Charleroi, above the Franco-Belgian border.

On the map, smaller blue mushroom clouds showed expected Nato targets - most of them relatively precise attacks - including strikes on Warsaw and Prague. The map dates from a time when the balance of power was radically different from now. In Washington the vacillating Jimmy Carter was suffering a series of defeats - the Iranian revolution and the subsequent seizure of the United States embassy in Teheran. Britain was at a low ebb, racked by strikes, and just putting its faith in Margaret Thatcher.

The Kremlin, however, was stretching its muscles - preparing for its ill-fated takeover of Afghanistan. Perhaps because the map shows a limited war game exercise, entitled Seven Days to the River Rhine, rather than full invasion plans, troops stop at the Rhine, and there are no attacks or bomb strikes on Britain, or on France. Large blue Nato nuclear bombers are shown flying out of bases in East Anglia, and squadrons of Nato fighters are shown scrambling from Danish bases into combat over the Baltic.

The decision to unveil the Warsaw Pact documents is one of the first moves of Poland's new conservative government. Mr Sikorsky described it as an attempt to draw a line under the country's Communist past, and "educate" the Polish public about the old regime. He did not deny that the opening of the archives will be seen as a provocation in Moscow. Russian-Polish relations have sharply deteriorated recently, amid rows over a planned oil pipeline, and Polish support for democratic revolutions in Russia's backyard, first in Ukraine, and now Belarus.

Mr Sikorsky, a former dissident who studied at Oxford University, said: "These are documents that are crucial for educating the public, and showing how Poland was kept as an unwilling ally of the Soviet Union. This government wants to end the post-Communist period. "It's important for citizens to know who was a hero, and who was a villain. It is important for the civic health of society to make these things public."

The files being released would include documents about "Operation Danube", the 1968 invasion of Czechoslovakia. They also included files on an army massacre of Polish workers in Szczecin in the 1970s, and from the martial law era of the 1980s.