Born in Landsberg am Lech, Bavaria as Wilhelm Leeb, he joined the Bavarian Army in 1895 as an officer cadet. After being commissioned a lieutenant of artillery, Leeb served in China during the Boxer Rebellion. He later attended the Bavarian War Academy in Munich (1907 - 1909) and served on the General Staff in Berlin (1909 - 1911). Promoted to captain, Leeb served as a battery commander in the Bavarian 10th Field Artillery Regiment at Erlangen (1912 - 1913).
At the outbreak of World War I, Leeb was on the General Staff of the Bavarian I Corps, then served with the Bavarian 11th Infantry Division. Upon promotion to major, Leeb was transferred to the Eastern Front in the summer of 1916. The following year, he was appointed to the staff of Crown Prince Rupprecht of Bavaria. On May 29, 1916, for his military achievements on May 2, 1915, Leeb received the Knight's Cross of the Military Order of Max Joseph. This was the Bavarian equivalent of the Prussian Pour le Mérite, and its receipt elevated Leeb to the ranks of nobility: on June 21, 1916, he received a patent of nobility, which changed his name by adding the title "Ritter" ("knight") and the German nobiliary particle "von" ("of").
After the war, Ritter von Leeb remained in the Reichswehr, the 100,000-man army permitted Germany under the Treaty of Versailles. In 1923, he was involved in putting down the Nazi Beer Hall Putsch. Then, before the rise of Adolf Hitler and the Nazi Party, von Leeb commanded Wehrkreis VII ("Military District VII", which covered Bavaria) as a lieutenant-general.
Hitler was not fond of von Leeb because of the general's anti-Nazi attitudes and religious convictions, and retired von Leeb in 1938 after promoting him to the rank of colonel general. But von Leeb was recalled to duty in July of the same year and made commander of the Twelfth Army, which took part in the occupation of the Sudetenland. Afterwards, he was pensioned off again.
In the summer of 1939, von Leeb was again called back into service and given command of Army Group C. During the Battle of France, his troops broke through the Maginot Line. For his role in this victory, von Leeb was promoted to the rank of Field Marshal (generalfeldmarschall) in July, 1940, and awarded the Knight's Cross.
Now having Hitler's confidence, von Leeb was given command of Army Group North and responsibility for the northern sector in Operation Barbarossa, the invasion of the Soviet Union. Von Leeb was to destroy the Soviet units in the Baltic region and capture all Soviet naval bases on the Baltic Sea. When the invasion began on June 22, 1941, von Leeb's armies met with outstanding success against an overwhelmed Soviet force. By the end of September, his army had advanced 900 kilometers into the Soviet Union and surrounded Leningrad, though he failed to capture the city.
The turning point in the defeat of the German attempt to capture Leningrad was the battle of Tikhvin in October through December 1941. At Tikhvin the Red Army, for the first time in World War II, inflicted a large-scale defeat on the Wehrmacht in ground warfare.
Encouraged by easy victories over the disorganized and poorly led Red Army at the beginning of the war and in hope of a quick capture of Leningrad, Ritter von Leeb had rushed his armies to Tikhvin, a key city on the road to Leningrad. A victory would allow the Germans to shift many of their troops from the north to Army Group Centre, to participate in a decisive attack on Moscow. The Germans, having numerical superiority in tanks over the Russians, succeeded in occupying Tikhvin on November 8. But the newly-appointed commander of the Soviet 4th Army, Kirill Meretskov, slowed and then stopped the Germans by applying active defense and constant counterattacks. Meretskov then took the offensive and on December 10 recaptured Tikhvin.
In the midst of the battle, Stavka (the Soviet high command) ordered Meretskov to organize a new Volkhov Front. By December 30, he had forced von Leeb back to the positions from which the Germans had begun their Tikhvin offense. According to one of the leading historians of the Eastern Front, David Glantz, "the concept of blitzkrieg failed for the first time in the Second World War[,] . . . anticipating" the Soviet victory at Moscow.
Soviet victory in the battle at Tikhvin directly aided the Red Army in the battle of Moscow. Instead of being able to send units from Army Group North to Army Group Centre, the Germans were compelled to move reinforcements in the opposite direction. According to Glantz, "[d]uring this most critical period of the war, 32 percent of the Wehrmacht's forces operating north of the Pripiat Marshes, including almost two full panzer groups, were tied down in combat along or adjacent to Tikhvin". The Wehrmacht lost 45,000 troops in the battle.
When von Leeb failed to capture Leningrad quickly, Hitler impatiently commented, "Leeb is in a second childhood; he can't grasp and carry out my plan for the speedy capture of Leningrad. He fusses over his plan of assuming the defensive in the northwestern sector and wants a drive in the center on Moscow. He's obviously senile, he's lost his nerve, and like a true Catholic he wants to pray but not [to] fight."
An old-school German general, von Leeb did not take well to having his command managed from afar by Hitler, whom he considered an armchair general. It is sometimes stated that Hitler fired Leeb, but this is incorrect: in January, 1942, von Leeb asked Hitler to relieve him of his command, and Hitler complied. It was officially announced that von Leeb had stepped down due to illness, not because of his defeat. Colonel-General Georg von Küchler assumed command of Army Group North, and Hitler never employed von Leeb again.
Von Leeb's attitude towards the Nazi regime was ambivalent: in spite of his open contempt for Hitler and the dictator's cronies, he did accept a present of 250,000 Reichsmarks for his sixty-fifth birthday in 1941. In 1944, von Leeb allowed the Nazis to use his popularity for propaganda purposes, when he was presented with a great Bavarian estate worth 638,000 Reichsmarks. After the failed July 20 plot to assassinate Hitler in 1944, von Leeb sent an affirmation of loyalty to the dictator.
After the war, von Leeb was tried by a American military tribunal in Nuremberg in the High Command Trial. Due to a confusion of documents, von Leeb was found guilty on one of four charges and sentenced to three years imprisonment; but he was released after the judgment because he had already spent more time in custody. He spent his last years living quietly with his family until his death in Füssen in 1956.