While his early years did not point toward a military career, Erich nevertheless entered the Royal Cadet School at Plön as a 12-year old boy. There he was studious and withdrawn, developing within himself the iron discipline which would serve him later during most of his military career. After two years in Plön, he transferred to the military academy at Gross-Lichterfelde near Berlin, and in 1882, at the age of seventeen, was commissioned a Leutnant (junior lieutenant). His first posting was at Wesel where he served for about five years in Infantry Regiment Herzog Ferdinand von Braunschweig (Eighth Westphalian) No. 57.

He then did a 3-year stint from 1887-90 in Wilhelmshaven with an elite unit of naval infantry troops, serving on the Niobe, the Baden, and the Kaiser, and sailing throughout Scandinavia and the British Isles. With a promotion to Oberleutnant (senior lieutenant), he spent a short time in Frankfurt an der Oder attached to Leib-Grenadier-Regiment Nr. 8, but was soon sent to the War College in Berlin for a three-year course with Russian as his main subject. In 1894, having done well with the language, he was sent to Russia to as a  military observer. He did his job well enough that on his return to Germany he was promoted to Hauptmann (captain) and sent to the Great General Staff.

In 1896, Captain Ludendorff was transferred to the VI. Corps in Magdeburg, then in 1898 he served as a company commander with Infantry Regiment No. 61 (8. Pomeranian). In 1901 he joined the staff of 9th Infantry Division in Glogau, commanded by General von Eichhorn, who was to become one of Ludendorff's subordinates during the war. As a major, he was sent back to the Great General Staff in 1904 to work under Count Alfred von Schlieffen. Ludendorff's task as part of the Second Department was the prepare the Imperial Army for mobilization. When Helmuth von Moltke replaced Schlieffen, Ludendorff was soon promoted to chief of the Second Department.  He ardently pressed for improved field communications and additional troops, heavy artillery, and aircraft. Many German political authorities did not look favorably upon his straight-forward manner, however, and Ludendorff's scheming and attempts to by-pass his chain of command made him many enemies in Berlin.

In the meantime, Erich met Margarethe Pernet Schmidt, the daughter of a wealthy industrialist, and quickly convinced her to leave her husband so that they could marry. Margarethe brought with her three sons and a daughter. They never had children of their own, but Erich treated Margarethe's as his own. Because of the waves he had made Berlin, he and his new family were transferred to a relatively obscure posting in Düsseldorf. Here, as a newly-promoted colonel, he took command of Niederrheinisches Fuesilier Regiment Nr. 39.  During the months leading up to the war, he was promoted to major general and then transferred to command an infantry brigade in Strasbourg. In March 1914, Ludendorff's mother died, with apparently little effect on him. He was also still strongly disliked back in the capital, and with the threat of war, instead of being assigned as an army chief of staff, his mobilization orders had him serving as Second Army quartermaster general under Karl von Bülow.

At the Hannover train station on the morning of 23 August 1914, a most unlikely but successful and historic partnership was formed  -- von Hindenburg the solid old soldier from an aristocratic Prussian background, and the younger, more volatile Ludendorff of more humble beginnings. They immediately began devising a strategy to save the Eighth Army and shore up the Eastern Front from a certain Russian invasion. Most of their plan had already been worked out and implemented, however, by Eighth Army operations officer Max Hoffmann. Although von Hindenburg and Ludendorff were given the immediate credit for the tremendous victory at Tannenberg, where the Germans crushed the Russian Second Army, historians have largely decided that most of the credit was due to Hoffmann's expertise. The dynamic duo of Hindenburg-Ludendorff were nonetheless on their way to becoming cult heroes back home, a factor which would continually raise its head during the Great War and even on into the years leading up to the Second World War.

By early November 1914, von Hindenburg and the newly-promoted Lieutenant General Ludendorff exercised supreme command of all Germans troops in the East from their headquarters Ober-Ost.  More victories followed on the Eastern Front with von Hindenburg giving his automatic approval to Ludendorff and Hoffmann's assault plans against the Russians. With Falkenhayn's failure at Verdun, von Hindenburg was sent to replace him in August 1916 as Chief of General Staff. Ludendorff naturally accompanied him, rejecting however the title of Second Chief. Instead, he created his own misleading designation as Erster Generalquartiermeister, First Quartermaster General. Continuing as von Hindenburg's deputy, he was assured that he'd have joint responsibility in all military decision making. At this point, Ludendorff was in fact the most authoritative military leader and was well on his way to controlling Germany's political scene as well.

Two weeks later, General of Infantry Erich Ludendorff fled in disguise to Sweden where he penned My War Memories, but he returned to Germany and its volatile political scene by early 1919. Pressing ever further to the right, he then participated in the failed Kapp Putsch of 1920, as well as Hitler's Beer Hall Putsch in 1923. After divorcing his wife, Erich married Mathilde Spiess in 1926 and became increasingly involved in the occult, expressing agitation towards Jews, Catholics, and Free-Masons. He had also become bitter enemies with von Hindenburg. In 1936 he wrote Total War which expounded on his theory that modern war involved the whole nation. On 20 December 1937, at the age of 72, the most influential German leader during the Great War went to his deathbed in Tutzing, Bavaria.  Although Ludendorff was a member of the Nazi Party, he did warn of Hitler's tyranny shortly before his death. Despite this, Hitler paid final tribute to him by walking behind his swastika-draped casket.