Question: What year did Heinrich Himmler join the unit that used the concept of Wehrbauer to refer to soldiers designated as settlers for the lands conquered during the German invasions of the Soviet Union and Poland?

Context paragraphs:
Hegewald (colony): Hegewald was a short-lived German colony during World War II, situated near Zhytomyr in Reichskommissariat Ukraine.  It was repopulated in late 1942 and early 1943 by the ethnically German settlers classified as "Volksdeutsche"; transferred from occupied territories of Poland, Croatia, Bessarabia, and the Soviet Union to an area earmarked for the projected Germanization of the Ukrainian lands.  The plans were prepared months in advance by the SS, RKFDV and VoMi, but major problems with supplies occurred right from the region's initial establishment.  Heinrich Himmler's original plans to recruit settlers from Scandinavia and the Netherlands were unsuccessful.

Ethnic cleansing of Zamojszczyzna by Nazi Germany: The ethnic cleansing of Zamojszczyzna by Nazi Germany (German: "Aktion Zamosc" , also: "Operation Himmlerstadt") during World War II was carried out as part of a greater plan of forcible removal of the entire Polish populations from targeted regions of occupied Poland in preparation for the state-sponsored settlement of the ethnic German "Volksdeutsche".  The operation of mass expulsions from Zamojszczyzna region around the city of Zamość (now in Lublin Voivodeship, Poland) was carried out between November 1942 and March 1943 on direct order from Heinrich Himmler.  It was preplanned by both, Globocnik from Action Reinhard and Himmler, as the first stage of the eventual murderous ethnic cleansing ahead of projected Germanization of the entire General Government territory.

List of ambassadors of Russia to Poland: Poland and Russia had exchanged diplomatic missions for centuries.  The first ambassador in the modern meaning of this word, from Poland to Russia, was Antoni Augustyn Deboli, in late 18th century.  After the period of partitions of Poland, in 1918, relations were established between the Second Polish Republic and Soviet Union.  After Soviet invasion of Poland in 1939 those relations were broken, to be briefly reestablished in 1941 after the German invasion of the Soviet Union, when the Soviet Union and Polish government in exile agreed to cooperate against their common enemy, Nazi Germany.  Those relations were broken in 1943 after discovery of the Katyn massacre.  From that point onward, Soviet Union created its own puppet Polish government, which had its "ambassadors" in the Soviet Union.  In 1989 the People's Republic of Poland was transformed into the modern Poland; in 1991, Soviet Union was transformed into modern Russia.

Schutzstaffel: The Schutzstaffel (SS; also stylized as with Armanen runes; ] ; literally "Protection Squadron") was a major paramilitary organization under Adolf Hitler and the Nazi Party (NSDAP) in Nazi Germany, and later throughout German-occupied Europe during World War II.  It began with a small guard unit known as the "Saal-Schutz" (Hall-Protection) made up of NSDAP volunteers to provide security for party meetings in Munich.  In 1925, Heinrich Himmler joined the unit, which had by then been reformed and given its final name.  Under his direction (1929–45), it grew from a small paramilitary formation to one of the most powerful organizations in Nazi Germany.  From 1929 until the regime's collapse in 1945, the SS was the foremost agency of security, surveillance, and terror within Germany and German-occupied Europe.

Katrin Himmler: Katrin Himmler (born 1967) is a German author.  She is the granddaughter of Ernst Himmler (1905-1945), who was the younger brother of Heinrich Himmler, one of the leading figures of Nazi Germany.  Therefore, she is the great-niece of Heinrich Himmler.  She is the author of "Die Brüder Himmler: Eine deutsche Familiengeschichte", published in English as "The Himmler Brothers: A German Family History".

Wehrbauer: Wehrbauer (] , "soldier peasant") was a concept used by the "Schutzstaffel" (SS) of the Nazi Party to refer to soldiers designated as settlers for the lands conquered during the German invasions of the Soviet Union and Poland.

List of Ambassadors of Poland to Russia: Poland and Russia had exchanged diplomatic missions for centuries.  The first ambassador in the modern meaning of this word, from Poland to Russia, was Antoni Augustyn Deboli, in late 18th century.  After the period of partitions of Poland, in 1918, relations were established between the Second Polish Republic and Soviet Union.  After Soviet invasion of Poland in 1939 those relations were broken, to be briefly reestablished in 1941 after the German invasion of the Soviet Union, when the Soviet Union and Polish government in exile agreed to cooperate against their common enemy, Nazi Germany.  Those relations were broken in 1943 after discovery of the Katyn massacre.  From that point onward, Soviet Union created its own puppet Polish government, which had its "ambassadors" in the Soviet Union.  In 1989 the People's Republic of Poland was transformed into the modern Poland; in 1991, Soviet Union was transformed into modern Russia.

Gestapo–NKVD conferences: The Gestapo–NKVD conferences were a series of security police meetings organized in late 1939 and early 1940 by Germany and the Soviet Union, following their joint invasion of Poland in accordance with the Molotov-Ribbentrop Pact.  The meetings enabled both parties to pursue specific goals and aims as outlined independently by Hitler and Stalin, with regard to the acquired, formerly Polish territories.  The conferences were held by the Gestapo and the NKVD officials in several Polish cities.  In spite of their differences on other issues, both Heinrich Himmler and Lavrentiy Beria had similar objectives as far as the fate of the prewar Poland was concerned.

List of Polish cities damaged in World War II: As the German army retreated during the later stages of the Second World War, many of the urban areas of what is now Poland were severely damaged as a result of military action between the retreating forces of the German Wehrmacht and advancing ones of the Soviet Red Army.  Other cities were deliberately destroyed by the German forces.  One of the most famous of these planned destructions was the razing of Warsaw, the capital of Poland.  While extensively damaged by the failed Warsaw Ghetto Uprising and Warsaw Uprising, the city later underwent a planned demolition by German forces under order from Adolf Hitler and high officials within the Nazi government.  On 17 October 1944, SS chief Heinrich Himmler famously stated, "The city must completely disappear from the surface of the earth and serve only as a transport station for the Wehrmacht."  Before they were stopped by the advancing Red Army, 85% of the city had been taken out.  Warsaw was far from the worst off after the Nazi retreat; 97% of Jasło and 100% of Polanów were reduced to rubble.  Other towns such as Wałcz fared better, with only a quarter of the city being destroyed.  Ancient historical buildings in Polish cities were not spared; for example, Trzemeszno's Romanesque basilica of 1130-45 was burnt down in 1945.

Ukrainian People's Militia: Ukrainian People's Militia or the Ukrainian National Militia (Ukrainian: "Українська Народна Міліція" ), was a paramilitary formation created by the Organization of Ukrainian Nationalists (OUN) in the General Government territory of occupied Poland and later in the Reichskommissariat Ukraine during World War II.  It was set up in the course of the 1941 Operation Barbarossa following the Nazi German attack on the Soviet positions in eastern Poland.  The formation, created in June 1941, preceded the official founding of the Ukrainian Auxiliary Police in mid-August 1941 by Heinrich Himmler.  There is conclusive historical evidence indicating that members of the Ukrainian Militia took a leading role in the 1941 Lviv pogroms, resulting in the massacre of 6,000 Polish Jews, after the German army reached Lwów (Lemberg) at the end of June in Soviet-occupied eastern Poland (now Lviv, Ukraine).  Initially the Ukrainian militia acted independently, with the blessings of the SS, but later were limited to joint operations ("Aktionen") with German units or otherwise functioned directly under the Nazi command.

Supporting paragraphs: Wehrbauer Schutzstaffel
Answer: 1925