Poland is risking further strains in relations with Russia by throwing open Cold War-era archives that include a 1979 Soviet retaliation plan that envisaged nuclear strikes on western European cities in the event of a war with NATO.

The map foresaw the nuclear annihilation of Poland and was dotted with red mushroom clouds over the German cities of Munich, Cologne, Stuttgart and the site of NATO headquarters in Brussels, Belgium.

It was revealed Friday by Polish Defense Minister Radek Sikorski, a staunch anti-communist who went into exile in Britain in the 1980s to oppose Poland’s Moscow-backed communist rulers.

By declassifying some 1,700 volumes of a Soviet-led military bloc’s files, Sikorski and Poland’s other new conservative leaders risk antagonizing Russian leaders, who rue the loss of their superpower status with the disintegration of the Soviet Union.

"This could worsen Russian-Polish relations," said Fyodor Lukyanov, editor of the magazine Russia in Global Affairs. "At this point, there is no more destructive topic for Russian-Polish relations than the historic one."

Historians have known about Moscow’s communist-era willingness to make Poland a nuclear battlefield in the event of war with the West, but the plan’s disclosure brings the vivid facts to the wider public.

The entire trove of information in the archives, which also includes documents on the Warsaw Pact’s 1968 invasion of Czechoslovakia to crush a democracy movement, is expected to be made public in January, meaning other surprises could surface.

Led by the Soviet Union, the Warsaw Pact was formed in the Polish capital in 1955 as the communist bloc’s counterbalance to NATO. It was dissolved in 1991 after the fall of communism.

Leon Kieres, head of Poland’s National Remembrance Institute, which will take over the archives from the Defense Ministry, said he had not yet seen all the documents and it wasn’t immediately clear what they hold.

By releasing them, Poland is making the point that Moscow no longer pulls the strings here.