The Supreme Commander of All German Forces in the East (German: Oberbefehlshaber der gesamten Deutschen Streitkräfte im Osten), also known by its German abbreviation as Ober Ost, was both a high-ranking position in the armed forces of the German Empire as well as the name given to the occupied territories on the German section of the Eastern Front of World War I, with the exception of Poland. It encompassed the former Russian governorates of Courland, Grodno, Vilna, Kovno and Suwałki. It was governed in succession by Paul von Hindenburg and Prince Leopold of Bavaria. It was abandoned after the end of World War I.

Ober Ost was set up by Kaiser Wilhelm II in November 1914, initially under the command of Paul von Hindenburg, a Prussian general who had come out of retirement to achieve the German victory of the Battle of Tannenberg in August 1914 and became a national hero. When the Chief of the General Staff Erich von Falkenhayn was dismissed from office by the Kaiser in August 1916, Hindenburg took over at the General Staff, and Prince Leopold of Bavaria took control of the Ober Ost.

By October 1915, the Imperial German Army had advanced so far to the east that central Poland could be put under a civil administration. Accordingly, the German Empire established the Government General of Warsaw and the Austro-Hungarian Empire set up the Government General of Lublin. The military Ober Ost government from then on controlled only the conquered areas east and north of central Poland.

After the signing of the Treaty of Brest-Litovsk of March 1918, the Ober Ost effectively spanned present-day Lithuania, Latvia, Belarus, parts of Poland, and Courland, all of which had been part of the Russian Empire.

Ober Ost governed in a very strict and often cruel way. The movement policy (Verkehrspolitik) divided the territory without regard to the existing social and ethnic organization and patterns. Movement between the districts was forbidden, which destroyed the livelihood of many merchants and prevented people from visiting friends and relatives in neighboring districts. The Germans also tried to "civilize" the people in the Ober Ost-controlled land, attempting to integrate German ideals and institutions with the existing cultures. They constructed railroads but only Germans were allowed to ride them and schools were established and staffed with German instructors.

In 1915, when large territories came under Ober Ost's administration as a result of military successes on the Eastern Front, Erich Ludendorff, von Hindenburg's second-in-command, set up a system of managing the large area now under its jurisdiction. Although von Hindenburg was technically in command, Ludendorff had actual control of the administration. There were ten staff members, each with a specialty (finance, agriculture, etc.). The area was divided into the Courland District, the Lithuania District and the Bialystok-Grodno District, each overseen by a district commander. Ludendorff's plan was to make Ober Ost a colonial territory for the settlement of his troops after the war and to provide a haven for German refugees from Russia. Ludendorff quickly organized Ober Ost so that it was a self-sustaining region, growing all its own food and even exporting surpluses to Berlin. The largest resource was one that Ludendorff was unable to exploit effectively: the local population had no interest in helping obtain a German victory, as it had no say in the government and was subject to increasing requisitions and taxes.

There were many problems with communication with local persons within the Ober Ost. Among the upper-class locals, the soldiers could get by with French or German, and in large villages, the Jewish population would speak German or Yiddish, "which the Germans would somehow comprehend". In the rural areas and amongst peasant populations soldiers had to rely on interpreters who spoke Lithuanian, Latvian or Polish. The language problems were not helped by the thinly-stretched administrations, which would sometimes number 100 men in areas as large as Luxembourg. The clergy at times had to be relied upon to spread messages to the masses since that was an effective way of spreading a message to people who speak a different language. A young officer-administrator named Vagts related that he listened (through a translator) to a sermon by a priest who told his congregation to stay off highways after nightfall, hand in firearms and not to have anything to do with Bolshevist agents, exactly as Vagts had told him to do earlier.

The uncertain situation caused by the Russian October Revolution in 1917 and the Treaty of Brest-Litovsk in March 1918 made some indigenes elect Duke Adolf Friedrich of Mecklenburg as head of the United Baltic Duchy and the second duke of Urach as king of Lithuania, but those plans collapsed in November 1918.

The Ober Ost was divided into three Verwaltungsgebiete (administrative territories): Kurland, Litauen, and Bialystok-Grodno. Each was, like Germany proper, subdivided into Kreise (districts); Landkreise (rural districts) and Stadtkreise (urban districts). In 1917 the following districts existed:

Bialystok-Grodno	Kurland
Alekszyce	Bauske
Bialystok, Stadtkreis	Doblen
Bialystok, Landkreis	Goldingen
Bielsk	Grobin
Grodno, Stadtkreis	Hasenpot
Grodno, Landkreis	Libau, Stadtkreis
Lida, Stadtkreis	Mitau, Landkreis
Ost	Talsen
Planty	Tuckum
Radun	Windau
Sokolka
Swislocz
Wasilischky
Wolkowysk

Litauen
Augustow	Rossienie
Birshi	Russisch-Krottingen
Johanischkele	Saldugischki
Kiejdany	Schaulen
Koschedary	Schirwinty
Kowno, Stadtkreis	Sejny
Kowno, Landkreis	Siady
Kupzischki	Skaudwile
Kurszany	Suwalki
Maljaty	Telsze
Mariampol	Uzjany
Okmjany	Wiezajcie
Olita	Wilkomierz
Podbrodzie	Wilna, Stadtkreis
Pojurze	Wilna, Landkreis
Poniewiez	Wladislawow
Rakischki	Wylkowyschki

The total area was 108,808 km (42,011 sq mi), containing a population of 2,909,935 (by the end of 1916).

• the 10th Army (10. Armee or Armeeoberkommando 10), Commanding Officer Erich von Falkenhayn, Grodno
• the Army Group Mackensen (Heeresgruppe Kiew)

With the end of the war and collapse of the empire, the Germans started to withdraw, sometimes in a piecemeal and disorganized way, from Ober Ost around late 1918 and early 1919. In the vacuum left by their retreat, conflicts arose as various former occupied nations declared independence, clashing with the various factions of the Russian Revolution and subsequent Civil War, and with each other. For details, see:

• Soviet westward offensive of 1918–19, part of the Polish–Soviet War (the largest of the resulting conflicts)
• Ukrainian–Soviet War and Polish–Ukrainian War
• Estonian War of Independence
• Latvian War of Independence
• Lithuanian Wars of Independence

The Lithuanian historian Vėjas Gabrielius Liulevičius postulates in his book War Land on the Eastern Front: Culture, National Identity, and German Occupation in World War I, that a line can be traced from Ober Ost's policies and assumptions to Nazi Germany's plans and attitudes towards Eastern Europe. His main argument is that "German troops developed a revulsion towards the 'East' and came to think of it as a timeless region beset by chaos, disease and barbarism", instead of what it really was, a region suffering from the ravages of warfare. He claims that the encounter with the East formed an idea of "spaces and races", which needed to be "cleared and cleansed". Although he has garnered a great deal of evidence for his thesis including government documents, letters and diaries in German and Lithuanian, there are still problems with his work. For example, he does not say much about the reception of German policies by native populations. Also, he "makes almost no attempt to relate wartime occupation policies and practice in Ober Ost to those in Germany's colonial territories overseas".

• Lebensraum
• Reichskommissariat Ostland

• Figes, Orlando (1998). A People's Tragedy: the Russian Revolution, 1891–1924. New York: Penguin Books. ISBN 0-670-85916-8.

• Davies, Norman (2003) [1972]. White Eagle, Red Star: The Polish–Soviet War, 1919–20 (2nd ed.). London: Random House. ISBN 0-7126-0694-7.
• Schwonek, M. R. (January 2001). "Book Reviews: War Land on the Eastern Front: Culture, National Identity, and German Occupation in World War I by Vejas, Gabriel Liulevicius". The Journal of Military History. 65 (1). Lexington, Virginia: Virginia Military Institute and the George C. Marshall Foundation: 212–213. doi:10.2307/2677470. ISSN 0899-3718. JSTOR 2677470.
• Stone, Norman (1975). The Eastern Front, 1914–1917. New York: Charles Scribner's Sons. ISBN 978-0-68414-492-4.

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