His taciturn nature and great personal reserve led to the nickname "Sphinx." Son of a Prussian general, he began his career in 1885 in the Kaiser Alexander Guard Grenadiers having completed the Gymnasium with an Abitur, an uncommon attainment. Literature was his strong suit. In 1893 he married Dorothea Fabian. They had no children, instead travelling extensively when on leave, with England and the Mediterranean basin among their favorites. He finished the Kriegsakademie 3rd in his class in 1896. Transfer to the General Staff Corps followed, with alternating service between line and staff positions. In each military assignment his reputation grew, and when war came in 1914, he was chief of staff of the III Army Corps in Berlin.
Seeckt's corps marched to the Marne with the 1st Army, and when success eluded the German Army, his corps fell back on Vailly. Local attacks here and at Soissions under his leadership made him a name in the General staff. In March 1915 he was named chief of staff of the newly organized 11th Army under General v. Mackensen which went east to Galicia. The 11th Army underwent its baptism of fire at Gorlice-Tarnow a month later, capturing 140,000 Russians in 12 days, occupying much of Poland and securing Silesia. The Kaiser presented Seeckt with the Pour le Meritè. By the end of June, Lemberg had fallen to the 11th Army whose prisoner bag now exceeded a quarter million. The 11th Army had advanced 300 kilometres. Mackensen became a field marshal; Seeckt received an accelerated promotion to brigadier. Further operations followed, driving the Russians out of Poland and capturing Brest-Litowsk. In September 1915 Seeckt and Mackensen travelled to the Temesvar as "Army Group Mackensen" whose function was to defeat Serbia and open the lines of communication through the Balkans to Turkey. German, Austrian and Bulgarian troops participated. Bulgaria's entry into the war made the difficult crossings of the Danube and Save Rivers against the tested Serbs easier, but Army Group Mackensen made slow progress. The campaign ran from October to the end of November, with the German-Austrian-Bulgarian forces pushing the Serbs into Albania and Greece. Some 150,000 prisoners were taken, and Seeckt received the Oak Leaf to his Pour le Merite.
Army Group Mackensen sat in Bulgaria in the spring of 1916, its plans to attack the Allies in Salonica on hold because of the German offensive at Verdun. In response to the crisis caused by the Brusilov Offensive of June 1916, Falkenhayn and Conrad sent Seeckt to Galicia as chief of staff of the 7th Austro-Hungarian (k.u.k.) Army with orders to stem the Russian advance and restore confidence. Bad blood existed between the Austrians and Germans in the East, and Seeckt fell into a situation where he was neither wanted nor respected. He did not get along with his commanding general, General v. Pflanzer-Baltin, "never a friend to the Germans." But the real issue was the differing conceptions of the role of the chief of staff held by the two armies, summed up by Pflanzer-Baltin after the war. Seeckt, he wrote, "came, observed--and ordered," as if the commanding general did not exist. This relationship did not last long, for Seeckt became chief of staff of Army Group Archduke Karl, a newly formed army group charged with stemming the Russian advance. Seeckt got along much better with Archduke Karl, and after hard fighting, the Russians were stopped in the Carpathian Mountains. Archduke Karl's forces then joined with Falkenhayn's 9th Army in the Rumanian Campaign. In the middle of the final phase, Archduke Karl became Emperor of Austria, and Archduke Joseph took his place as army group commander. Through 1917 Seeckt remained as chief of staff of Army Group Archduke Joseph, a difficult position because of growing Austro-German hostility. Nonetheless, when Seeckt left for his next assignment, Archduke Joseph wrote that he could not imagine a better chief of staff.
In December 1917 Seeckt travelled to Istanbul to become chief of staff of the Turkish Army with the rank of Major General. The High Command had nominated Liman v. Sanders, but Turkish War Minister Enver Pasha had turned him down. The Palestine Front was the most active, with Allenby taking Jerusalem the week before Seeckt's arrival. Sanders took over the Palestine Front, creating an awkward situation. As chief of the Turkish General Staff, Seeckt was senior to Sanders; however, Seeckt was only attached to the Turkish Army but assigned to the German Military Mission in Turkey, which Sanders headed. The two did not get along. Seeckt's activities expanded into politics, which he bemoaned. German and Turkish interests drifted apart, especially in the Caspian Sea region which the German High Command wanted to exploit for war materiel, while the Turks had differing views. Owing to the campaigns in France in 1918, the Eastern Mediterranean theater took second place through out the first half of the year, but in mid-September the Allies broke out of Salonika and Allenby routed Liman's forces in Palestine. When Bulgaria dropped out of the war in October, Turkey's position was hopeless. On 30 October Turkey signed an armistice with the Allies, allowing the Germans thirty days to leave Turkey. Seeckt left on the 4th of November via the Black Sea and Odessa, arriving in Germany on the 13 of November.
Seeckt hardly welcomed the new Republic, but he made clear his desire to continue to serve "the Fatherland." Hindenburg asked Seeckt to go to Königsberg in January 1919 to oversee the evacuation of German troops from the Ukraine and East. His handling of this extraordinarily difficult situation led to his appointment to the German delegation at the Paris Peace Conference. In July 1919 he became chief of the general staff, and a year later, he headed (Chef der Heeresleitung) the post-war army until his retirement in 1926. In the midst of great political turmoil, he created what contemporaries felt was the world's best-trained and led military force. Following retirement, he entered politics and served in the Reichstag, wrote several books, and worked in China (1933-35) with Chiang Kai-shek as a military advisor. He died of heart disease. In spite of his considerable achievements in the First World War, his reconstruction of the post-war German army, the Reichswehr, is the basis of his fame today.
Seeckt wrote a number of articles and books in his retirement, chief among which is Gedanken Eines Soldaten (Thoughts of a Soldier), expanded edition, 1935. Seeckt's extensive papers exist in the German Military Archive in Freiburg. An older, two volume biography was done by his assistant General Friedrich von Rabenau, Hans von Seeckt: Aus Meinem Leben, (1866-1917) and Aus Seinem Leben, (1917-1936), 1938 and 1940. Rabenau used archival materials lost in the Second World War. The current, standard biography is Hans Meier-Welcker, Seeckt, 1967. Meier-Welcker headed Germany's Military-Historical Research Office. None of these works are available in English.