WHEN Nina, Baroness von Lerchenfeld, married the German cavalry officer Claus von Stauffenberg in Bamberg in 1933, her husband-to-be attended the ceremony in full uniform including steel helmet, explaining to his bride that “to be wed is to be on duty”. When she had asked why he had chosen her to be his wife, he replied that he judged her suitable to be mother of his children.

Little can either of them have guessed what demands such ideas of duty and parenting would eventually make. Stauffenberg, while an energetic participant in Germany’s military revival, gradually came to the conclusion that Hitler had to be assassinated in order to save Germany from utter ruin. And Nina, while not directly involved in the plot, was his regular confidante as he planned this perilous act.

When in July 1944 the briefcase bomb that Stauffenberg had planted near to Hitler at his HQ at Rastenburg in East Prussia narrowly failed to kill him, Stauffenberg was executed and his whole family imprisoned. Nina was separated from her children and feared she had lost them for ever. For the remainder of her life until her death, she was left both sustaining her family and trying to uphold the memory of her husband’s sacrifice in the midst of much public scrutiny.

She was born in Kaunas, Lithuania (then Kovno in Russia), in 1913. Her father was a well-connected former Bavarian royal chamberlain and her mother from the Baltic German aristocracy. She got to know Stauffenberg while she was still a teenager. His good looks and dashing cavalry uniforms doubtless had their appeal, but in other ways he must have seemed a distant figure, dedicated with his brothers to a mystical cult of ancient Germanic chivalry centred on the poet Stefan George. He had also imbibed the German officer’s traditional conviction that his institution, the Army, embodied his country. The period after their marriage was a heady one for German officers, as the Nazi takeover of power accelerated rearmament.

Nina angrily denied suggestions made after the war that Stauffenberg was initially enthusiastic about National Socialism — the Nazi leadership hardly corresponded to his vision of a German elite.

Yet Stauffenberg and his wife would have agreed with the Nazis’ determination to reverse the “shame” of the Versailles treaty that had punished Germany after the First World War, and they applauded the national revival amid what appeared to be European decline. Visiting England in 1936, Stauffenberg wrote to Nina that the country seemed like a fire that had gone out. And in 1940, after fighting in the campaign that forced France’s rapid capitulation, he wrote to her:

“If we teach our children that only constant struggle and constant striving for renewal can save us from decline . . . and that permanence, preservation and death are identical, then we shall have accomplished the greatest part of our national duty of education.”

At the same time Stauffenberg’s letters home at this time, quoted by his biographer Peter Hoffmann, speak of “sudden Führer decisions” likely to upset military planning. And when he went to work for the General Staff in Berlin, and learnt more of what the SS and others were doing to the Jews in Eastern Europe, his opposition to Hitler hardened, and he began to associate with sympathisers among the officer corps, senior officials and aristocrats.

He was badly wounded in Tunisia and lost the use of an eye. Nina remarked on his return in 1943 that he “seemed to be involved in a conspiracy”. This he confirmed, and she is said in one account to have joked that, with his eye patch, he was now the ideal person to carry it out. He replied that the less she knew the better. However, in subsequent months she was drawn into the plot. After visiting her husband in Berlin she had to take back to their home in Bamberg a rucksack full of compromising documents for discreet disposal.

By mid-1944 Stauffenberg was more determined than ever, telling a friend: “Now it is not the Führer of the country or my wife and four children who are at stake: it is the entire German people.” As he prepared to place the bomb on July 20, 1944, he tried to make contact with Nina, but it was impossible. She learnt of the failed attack on the radio on the 21st. By that time her husband was dead, executed in the courtyard of army headquarters in Berlin to which he had returned after planting the bomb, hoping to begin administering a post-Hitler state.

The Nazis were determined to wreak a widespread and highly personal revenge on the plotters. Himmler raged to SS leaders that the Stauffenberg family would be “exterminated down to the last member”. But the Nazi leadership’s orders were not always followed through as the war approached its end. Her four children were taken from her, given new names and taken to Thuringia, where there was talk of having them adopted by loyal Nazi families.

Nina herself was detained in various places, among them the Ravensbrück concentration camp, and gave birth to a fifth child while in custody in Frankfurt an der Oder in January 1945. At the end of the war she was reunited with her other children.

After the war she worked for better relations between the Germans and their American occupiers, and helped her children to build new lives in West Germany. The family military tradition was maintained: one of her sons became a general in the Bundeswehr.

Public interest in her husband’s actions and motives was constant. There was gratifying official recognition of her husband’s act as an example of a “better Germany”. But the stream of political speeches, books, films and TV programmes gave varying impressions of the plotters’ motives and the attitudes of their families. Nina for the most part maintained a dignified silence. But she gave some interviews, saying in one that she had seen her role as offering her husband support — “not standing in his way and not burdening him”. He had, she said, consciously taken a heroic path.

She is survived by her five children.

Nina von Stauffenberg was born on August 27, 1913. She died on April 2, 2006, aged 92.