Dating from 1979, the map reveals how Soviet forces could respond to a Nato assault by invading Germany, Belgium and the Netherlands.

Red and blue mushroom clouds are marked on the map, showing Soviet nuclear bombs raining down on cities including Brussels, Antwerp, Munich and Stuttgart, and Nato nuclear strikes on Warsaw and a line of Polish territory, cutting the country in two. The Nato objective was to halt a second wave of Soviet troops sweeping westwards from Russia. Polish military chiefs said yesterday that about two million people would have died in Poland alone. Meanwhile, Britain and France appeared to have escaped unscathed, so separate plans may have existed for them.

The right-wing Polish government sent a powerful political message by releasing the map from the military archives, reinforcing its tough, nationalistic and anti-Russian rhetoric.

The Law and Justice party emphasized that key figures in the previous social democratic government had been members of the Communist regime.

Radoslaw Sikorski, the Defence Minister, said there had been no prior discussions with Moscow about the release. Explaining how the Soviets had made Poland the main target for Nato, he argued: "We need to know about our past. Historians have the right to know the history of the 20th century. If people did some things they were not proud of, that will be an education for them too.

"I think it is very important for a democracy for the citizens to know who was who, who was the hero and who was the villain. On that basis we make democratic choices.

"I think it is also important for the health of civic society for morality tales to be told: that it pays to be decent and that if you do things that did not serve the national interest, one day it will come out and you might be called to account."

Mr Sikorski promised to release 1,700 documents including the statute of the Warsaw Pact, protocols from its political and military committees and documents relating to the suppression of the Prague Spring uprising in 1968.

The model for openness is that of the Gauck Institute in Berlin, which made public the files compiled by the Stasi, the East German secret police. "This government wants to end the post-Communist period in which the files of the Warsaw Pact were secret,'' Mr Sikorski said.

Asked whether the release of archive material would recreate social divisions, and antagonise those who regard Poland's last Communist leader, General Wojciech Jaruzelski, as a hero, Mr Sikorski replied bluntly: "He is not considered to be a hero by me.''

Interestingly, the Warsaw Pact training map illustrates a defensive military operation in response to a Nato nuclear strike, and the Soviet forces appeared to stop at the English Channel. French territory is also avoided, a fact which Waldemar Wojcik, head of Poland's central military archive, explained by the fact that France was outside Nato's integrated military command structure.

Britain does, however, feature on the map and Nato bombers are shown flying over Bridlington and Ipswich on the way to the Continent, as a separate force sweeps in from Denmark.

Mr Wojcik added that, on a visit to Washington, Polish military officials had seen plans from Nato that were "a mirror image" of the Warsaw Pact's own deadly war plan.