News of Marie von Clausewitz’s unexpected death in January 1836 reverberated within Prussia’s imperious court and circulated among Berlin’s spirited political salons. The shock also required her personal nurse, Luise Hensel, to deliver a detailed report to Marie’s close friend, the royal princess. Friedrich Wilhelm III, Prussia’s lethargic ruler, quickly responded offering his condolences to Madam von Clausewitz’s remaining family. “Even now I cannot come to peace with this sad story that interests all Berlin,” Hensel wrote in a letter, over a month after the tragic event.

Marie served as governess of the country’s future ruler, Emperor Friedrich III, in one of the highest civil positions a woman could achieve in a monarchical state. She died as a result of a preposterous medical mistake, and it was indeed her high rank that probably prompted the doctors to apply a heavy-handed and deadly series of bloodlettings. Strikingly in her accounts Luise Hensel did not mention the reason most people know Marie’s name today—as the widow of West’s most influential military theorist, Carl von Clausewitz. The nurse appears both unaware of Clausewitz’s seminal treatise, On War, and Marie’s crucial role as its editor and publisher after her husband’s untimely death in 1831. For her contemporaries, Marie was defined less by Clausewitz’s legacy but rather as a woman who occupied an important position in Prussian society. 

Yet even her important role, from a modern perspective, as editor and publisher of On War has remained understudied. Clausewitz died before completing the seminal treatise and many of the controversies surrounding his theory stem directly from its fragmentary state. These circumstances make Marie all the more interesting to scholars since her decisions cast a long shadow over the perception of her husband’s life work. One could easily conclude that this was just another case where women’s achievements throughout history have been ignored. The reality is more complicated, however. Only twenty-six of Marie’s letters to her husband and few essays were ever published, insufficient material for any thorough study, while the rest of her writings were considered lost. 

In 2012 the decision of the German aristocratic family Buttlar to deposit its archives in the Prussian Privy State Archives in Berlin, suddenly, changed this situation. The Buttlars are direct decedents of Marie’s brother Friedrich von Brühl (the Clausewitz couple were childless). In the dusty boxes, the archivist discovered the complete intimate correspondence between Carl and Marie. Among the documents especially valuable are 283 previously unknown letters that Marie wrote from 1807 to 1831. This sensational discovery finally allows scholars to study not only her influence over Clausewitz but also to open the field of military theory and history to new and engaging views.

Born Countess von Brühl, Marie was highly intelligent and unusually well educated for a woman of her time. She was raised in the immediate vicinity of the country’s future ruler Friedrich Wilhelm III. Marie’s father was his governor. Early on, she fostered close friendships with the most vibrant personalities of the era like Baron von Stein and Caroline von Berg. It was probably that combination of intellectual primacy and social prominence that first drew Carl von Clausewitz, a poor and unknown junior officer from the provinces, to the formidable, but rather plain-in-her-looks countess. 

Marie’s motives to elevate the liaison to a marriage (and it was mostly hers) were more complicated. The countess and the junior officer were truly in love but she still feared, as her letters and essays reveal, losing her independence. The countess had a relatively small but regular income and a clear perspective of achieving a prominent position as a courtier serving the ruling dynasty. Yet, contrary to the prevailing attitudes of the era Clausewitz treated Marie as an equal partner and conquered her heart.

The couple lived in the turbulent times after the French Revolution when the ideas of liberté, égalité, fraternité first captured Europe’s progressive minds. But then Napoleon’s imperialist policy gave rise to anti-French feelings and new-born nationalism throughout the continent. Politically active and superbly connected, Marie, and not Clausewitz, was a member of the radical patriotic circle that gave rise to Ferdinand von Schill's anti-Napoleonic revolt from 1809. Throughout the prolonged fighting in 1813-1815, she followed Clausewitz to the battlefield and spent extended periods in the military camp. Her writings from the period, the majority of them unpublished, reveal the everyday reality of war for women behind the battle lines. Often observed with suspicion by the official hierarchy, ladies of high status like Marie cared for the wounded soldiers and their family members and informed political elites back in the capital about the true developments on the field. 

The couple’s close intellectual collaboration came to fruition in the peaceful years after Napoleon’s final defeat in 1815. For sixteen years Clausewitz worked on his groundbreaking theory of war, usually in Marie’s presence. She served as his sounding board, researcher of historic facts, and secretary, as numerous passages throughout the remaining drafts of On War written in her hand bear witness. Marie was, Clausewitz wrote in jest, his “staff officer.”   

After his untimely death in 1831 from cholera, her editing decisions cast a long shadow over On War’s later interpretations. Marie decided to publish it with the latest revisions Clausewitz had envisioned but without intense rewritings or any changes that might have consolidated the text and made it an easier read. Indeed, as her little known Preface from 1834 to the Seventh Part of Posthumous Works suggests, Marie understood that this opened the text to multiple and often conflicting interpretations. Yet she still defended this decision because through these inevitable discussions, one would seek to “convey the truth … that was [Clausewitz]’s goal above all.” Thereby Marie suggested that particularly the unfinished character of the text, with all its deficiencies and conflicting ideas, should provoke debate through which an understanding of the complex phenomenon of war would emerge. 

It is an interpretation little understood and often ignored. Yet it is striking insightful, and may have contributed to the book’s influence.