After the invasion of the Soviet Union, he served in Einsatzgruppe A before becoming a commander of the Sicherheitspolizei (SiPo) and Sicherheitsdienst (SD) forces in Riga, Generalbezirk Lettland (today, Latvia).

[2] He completed his dissertation on the "instruction right of the employer" and received a doctor of law degree in December 1933 just after joining the Sturmabteilung (SA) on 14 November of that year.

[4][2] In May 1938, just after the Anschluss with Austria, Lange was transferred to the new Gestapo office in Vienna to supervise the takeover of the Austrian police system.

He was involved in the persecution of Viennese Jews, including the brutal attacks, arrests and looting of property that occurred during the Kristallnacht pogrom of November 1938.

[6] This was followed by an appointment as the deputy head of the office of the Inspector of the SiPo and SD in Wehrkreis (military district) IX, headquartered in Kassel.

On 5 June 1941, Lange was ordered to Pretzsch and the command staff of Einsatzgruppe A, headed by now SS-Brigadeführer und Generalmajor der Polizei Stahlecker.

[15] From the beginning of his involvement in Latvia, Lange gave orders to squads of Latvians, such as the Arajs Kommando, that the Germans had organised to carry out massacres in the smaller cities.

[16] Another local organisation receiving orders from Lange was the Vagulāns Kommando, which was responsible for the Jelgava massacres in July and August 1941.

[19] After the Nazi regime decided to deport Jews from Germany, Austria and Czechoslovakia to the east, Lange was in charge of receiving the deportees coming to Riga.

In this connection, on 8 November 1941, he issued detailed instructions to Hinrich Lohse, who was Reichskommissar Ostland, regarding the transport of 50,000 Jews to the east, with 25,000 going to Riga and 25,000 to Belarus.

[25] One of his last actions in Riga was in Sonderaktion 1005, the operation that used prisoners to exhume mass graves and burn the bodies of the victims of Nazi atrocities in an attempt to prevent the advancing Soviet forces from discovering them.

[27] The minutes of the meeting specifically noted that Lange was there as the representative (Vertreter) of the commander (Befehlshaber) of SiPo and SD forces in the Reichskommissariat Ostland, who at the time was SS-Brigadeführer Franz Walter Stahlecker.

[28] Heydrich viewed Lange's first-hand experience in conducting the mass murder of deported Jews, in Latvia, as valuable for the conference.

[28] Instead of Lange, Heydrich could have invited either Karl Jäger or Erich Ehrlinger, who commanded the SiPo and SD in Lithuania and Belarus respectively, and were responsible for similar massacres.

[28] In Ian Kershaw's biography Hitler 1936-1945 Nemesis, in the section of the book covering the beginnings of the Holocaust and the Wannsee Conference, the SS major is twice mistakenly referred to as Dr. "Otto Lange".

Reports of the exact circumstances of Lange's death vary, but he is said to have been killed on or around that date, either in combat or by suicide, and is buried in the Cmentarz Miłostowo w Poznaniu [wo] military cemetery in Poznań.

[33] He supervised the arrival of the transports, aided by SS-Obersturmbannführer Gerhard Maywald, whom historian Gertrude Schneider, a survivor of the Riga ghetto, describes as Lange's "sidekick".

Lange personally shot a young man, Werner Koppel, who he felt was not opening a railway car door fast enough.

[22] Schneider described Lange's appearance:Even though he was somewhat smaller and darker than the blond, blue-eyed Maywald, he looked very handsome in his fur-collared uniform coat and seemed every inch an officer and a gentleman.