Eastern Front fur
busby At the outbreak of war in 1914, Mackensen, aged 65, commanded the
XVII Army Corps, which became part of the
German Eighth Army in East Prussia, under General
Maximilian von Prittwitz, and then, 21 days later, under General
Paul von Hindenburg. Mackensen had his corps moving out on a 25 km march to the
Rominte River within fifty minutes of receiving his orders on the afternoon of 19 August 1914, after the
Imperial Russian Army had
invaded East Prussia. He led the XVII Corps in the battles of
Gumbinnen (20 August 1914),
Tannenberg (23 to 30 August 1914) and the
First Battle of the Masurian Lakes (2 to 16 September 1914), which drove the invading Russians out of most of East Prussia. On 2 November 1914, Mackensen took over command of the
Ninth Army from Hindenburg, who became Supreme Commander East (
Oberbefehlshaber Ost). On 27 November 1914, Mackensen was awarded the
Pour le Mérite, Prussia's highest military order, for successful
battles around Warsaw and
Łódź. By April 1915, the Russians had conquered much of western
Galicia and were pushing toward
Hungary. In response to the desperate pleas from Vienna, German Chief of Staff
Erich von Falkenhayn agreed to an offensive against the Russian flank by an Austro-German army under a German commander. The reluctant Austro-Hungarian supreme command agreed that the tactful Mackensen was the best choice for commanding the coalition army.
Army Group Mackensen (
Heeresgruppe Mackensen) was established, containing a new German
Eleventh Army, also under his command, and the Austro-Hungarian Fourth Army. As chief of staff, he was assigned
Hans von Seeckt, who described Mackensen as an amiable, "hands-on commander with the instincts of a hunter". His army group, which had an overwhelming advantage in
artillery, smashed through the Russian lines between
Gorlice and Tarnow and then continued eastward. Never giving the Russians time to establish an effective defence, it retook most of eastern Galicia, recapturing
Przemyśl and
Lemberg. The joint operation was a great victory for the
Central Powers, which advanced 310 km (186 mi), and the Russians
pulled out of all of Poland soon afterward. Mackensen was awarded oak leaves to his
Pour le Mérite on 3 June 1915 and was promoted to
field marshal on 22 June. He also received the
Order of the Black Eagle, Prussia's highest-ranking order of knighthood, as well as numerous honours from other German states – including the Grand Cross of the
Military Order of Max Joseph, the highest military honor of the
Kingdom of Bavaria, on 4 June 1915 – and from Germany's allies.
Serbian campaign In October 1915, a new
Army Group Mackensen (
Heeresgruppe Mackensen, which included the
German Eleventh Army, the
Austro-Hungarian Third Army and the
Bulgarian First Army), launched a renewed campaign against
Serbia. The campaign crushed effective military resistance in Serbia but failed to destroy the
Royal Serbian Army, half of which managed to
retreat to Entente-held ports in Albania and, after recuperation and rearmament by the French and the Italians, re-entered fighting on the
Macedonian front. When Mackensen returned to Vienna, he was honoured by a dinner and a personal audience with Emperor
Franz Joseph I of Austria and was decorated with the magnificently jeweled
Military Merit Cross 1st Class with Diamonds, a unique award for a foreigner. Mackensen appears to have had great respect for the Serbian Army and Serbs generally. Before departing to the Serbian front in 1915, he had spoken to his men: Then, a German and Austro-Hungarian army group that was commanded by Falkenhayn
broke into Wallachia through the
Vulkan Pass in the Transylvanian Carpathian Mountains while Mackensen crossed the Danube by seizing bridgeheads on the left bank to shield the Austro-Hungarian engineers who built the long pontoon bridge. The Romanian Army and its Russian allies were forced back between those pincers. After three months of war, two thirds of Romania was occupied by the Central Powers. The capital of Romania,
Bucharest,
was captured by the Central Powers on 6 December 1916, on his 67th birthday. He rode in on a white horse and moved into the Romanian royal palace. For that performance, on 9 January 1917, Mackensen was awarded the
Grand Cross of the Iron Cross and became one of only five recipients of that honour in the First World War. Since he now wore every Prussian medal, the Kaiser decided to name a battle cruiser after him, which became the first in a
new class. Mackensen became the military governor of the large part of Romania (mainly
Wallachia) that was occupied by the Central Powers. He proposed making a German prince the King of Romania, but the initiative fell through. His last campaign was an attempt to destroy the Romanian Army, which had been reorganised. During the
Battle of Mărăşeşti, both sides took heavy losses, but the Romanian Army emerged victorious. Mackensen maintained that he had never been defeated in battle, and he surely was the most consistently successful senior general on either side in World War I. By December 1917, the Russian Army had collapsed, and the Romanian Armed Forces were forced to sign the
Armistice of Focșani, followed by the
Treaty of Bucharest. On 11 November 1918, Germany signed an
armistice with the Allies under which it had to immediately withdraw all German troops in
Romania, the
Ottoman Empire,
Austria-Hungary and the
Russian Empire back to German territory and Allies to have access to those countries. ==Postwar==