Question: Eisenwerke Oberdonau was created after what annexation of Austria into Nazi Germany?

Context articles: Slovene Lands in World War II
Religion in Nazi Germany
Reichsgau Oberdonau
Arthur Seyss-Inquart
Eisenwerke Oberdonau
Anschluss
Gauliga Ostmark
Polish areas annexed by Nazi Germany
German Occupation Medals
1938 Polish ultimatum to Lithuania

World War II in the Slovene Lands started in April 1941 and lasted until May 1945.
 Slovenia was during World War II in a unique situation in Europe, only Greece shared its experience of being trisected, however, Slovenia was the only one that experienced a further step — absorption and annexation into neighboring Nazi Germany, Fascist Italy, and Hungary.
 The Slovene-settled territory was divided largely between Nazi Germany and the Kingdom of Italy, with smaller territories occupied by Hungary, and the Independent State of Croatia.
In 1933, prior to the annexation of Austria into Germany, the population of Germany was approximately 67% Protestant and 33% Catholic; while the Jewish population was less than 1%.
 A census in May 1939, six years into the Nazi era and after the annexation of mostly Catholic Austria into Germany, indicates that 54% considered themselves Protestant, 40% Catholic, 3.5% self-identified as ""gottgläubig"" (lit.
 "believers in God", often described as predominately creationist and deistic), and 1.5% as non-religious.
The Reichsgau Oberdonau (English: "[{Reichsgau]] Upper Danube") was an administrative division of Nazi Germany consisting of Upper Austria and parts of Southern Bohemia.
 Parts of the Salzkammergut were annexed from Styria.
   (in German: Seyß-Inquart; 22 July 189216 October 1946) was an Austrian Nazi politician who served as Chancellor of Austria for two days – from 11 to 13 March 1938 – before the "Anschluss" annexation of Austria by Nazi Germany, signing the constitutional law as acting head of state upon the resignation of President Wilhelm Miklas.
Eisenwerke Oberdonau (German for "Steel Works of Upper Danube") was a large steel and iron producing company, a holding of several steel works in southern Germany and Austria.
 Created after the Anschluss of Austria, it formed the part of the so-called "Reichswerke Hermann Göring AG" cartel, the main supplier of steel and iron for the German war industry during World War II.
 It is also argued that it was the largest steel mill complex in Europe at that time .
Anschluss (] 'joining') is the annexation of Austria into Nazi Germany on 12 March 1938.
 The word's German spelling, until the German orthography reform of 1996, was Anschluß and it was also known as the Anschluss Österreichs (   , German: "Austrian Annexation" ).
The Gauliga Ostmark, renamed Gauliga Donau-Alpenland in 1941, was the highest football league in Austria after its annexation by Germany in 1938.
 Shortly after the occupation, the Nazis reorganised the administrative regions in Austria, and the seven "Gaue" "Carinthia", "Niederdonau", "Oberdonau", "Salzburg", "Styria", "Vienna" and "Tyrol-Vorarlberg" replaced the country of Austria.
 From 1941, the northern-most region of the Kingdom of Yugoslavia, "Drava Banovina", became part of the "Gaue" "Carinthia" and "Styria".
Following the Invasion of Poland at the beginning of World War II, nearly a quarter of the entire territory of the Second Polish Republic was annexed by Nazi Germany and placed directly under the German civil administration.
 The rest of Nazi occupied Poland was renamed as the General Government district.
 The annexation was part of the "fourth" partition of Poland by Nazi Germany and the Soviet Union, outlined months before the invasion, in the Molotov-Ribbentrop Pact.
The German Occupation Medals were a series of awards, also known as the ""Flower War medals"", created to commemorate the annexation of Austria, Czechoslovakia and the Memelland by Nazi Germany in the interwar period.
 All three medals were designed by Professor Richard Klein, Director of the Munich School of Applied Arts and a favoured artist of the Nazi establishment.
The 1938 Polish ultimatum to Lithuania was an ultimatum delivered to Lithuania by Poland on March 17, 1938.
 The Lithuanian government had steadfastly refused to have any diplomatic relations with Poland after 1920, protesting the annexation of the Vilnius Region by Poland.
 As pre-World War II tensions in Europe intensified, Poland perceived the need to secure its northern borders.
 Five days earlier, Poland, feeling supported by international recognition of the annexation of Austria by Nazi Germany, decided to deliver an ultimatum to Lithuania.
 The ultimatum demanded that the Lithuanian government unconditionally agree to establish diplomatic relations with Warsaw within 48 hours, and that the terms be finalized before March 31.
 The establishment of diplomatic relations would mean a "de facto" renunciation of Lithuanian claims to the region containing its historic capital, Vilnius (known in Polish as Wilno).