WASHINGTON (WUSA9) -- U.S. Immigration and Customs Enforcement says thelong-lost diary of Alfred Rosenberg, a close confidant of Adolph Hitler, has been recovered after an extensive investigation by Homeland Security Investigations.

According to ICE officials, Rosenberg, one of the most notorious members of the Third Reich and of the Nazi Party during World War II, knew about "much of the planning for the Nazi racial state, mass murder of the Jewish people, planning and conduct of World War II and the occupation of Soviet territory." Officials say the RosenbergDiarycould give historians more information about what was happening during that time period.

Historian Jurgen Matthaeustalked about the discovery and the tone of the diary in a video released by ICE. You can see the video attached to this article. Matthaeus also talked about how Rosenberg was "an extremely committed idealogue," "sticking to his guns until the very end."

"Thanks to the tireless investigative work of HSI special agents, and years of perseverance by both the U.S. Attorney's Office for the District of Delaware and the U.S. Holocaust Memorial Museum, the long-lost Rosenberg Diary has been recovered, not in Germany but in the United States," said ICE Director John Morton in a statement released on Thursday. "This important record of the crimes of the Third Reich and the Holocaust is now preserved for all to see, study and learn from. The work of combating the international theft of cultural heritage is a key part of our work, and no matter how long these items may appear to be lost to history, that hard but important work will continue."

In the same press release, U.S. Holocaust Memorial Museum Director Sara J. Bloomfield, said, "The United States Holocaust Memorial Museum is thrilled to have recovered the diary of Alfred Rosenberg, a leading Nazi ideologue ... As we build the collection of record on the Holocaust, having material that documents the actions of both perpetrators and victims is crucial to helping scholars understand how and why the Holocaust happened. The story of this diary demonstrates how much material remains to be collected and why rescuing this evidence is such an important museum priority."

Alfred Rosenberg also wrote The Myth of the Twentieth Century,which contained thephilosophical underpinnings of national socialist ideology. Rosenberg was the head of the Nazi party's foreign affairs department and the Reich Minister for the Occupied Eastern Territories. Officials say Rosenberg played a significant role in the mass murder of the Jewish people in the Occupied Eastern Territories, and the deportation of people to forced labor camps. Rosenberg also established and headed Einsatzstab Reichsleiter Rosenberg (Reichsleiter Rosenberg Taskforce) to loot cultural property throughout Europe.

Additionalyl, Rosenberg was a defendant at the Nuremberg Trials in Nuremberg, Germany from 1945 to 1946. He was found guilty on all four counts of the indictment for conspiracy to commit aggressive warfare, crimes against peace, war crimes and crimes against humanity. Rosenberg was hanged Oct. 16, 1946.

Allied forces seized the Rosenberg Diary along with other documents in 1945, say officials.Officials say a Dr. Robert M.W. Kempner, lawyer who fled Germany for the U.S. during the war, served as the eputy chief counsel and was the chief prosecutor in the "Ministries Case" at the Nuremberg Trials. He had access to the diary and after the trials, say officials, and against the law he removed the Rosenberg Diary with other documents and kept them until his death in 1993. Then, in November 2012, an art security specialist working withthe Holocaust Memorial Museum contacted the U.S. Attorney's Office for the District of Delaware and HSI special agents. Information from the specialist led to the location and recovery of The Rosenberg Diary pursuant to a warrant issued by the U.S. District Court for the District of Delaware.

HSI says more than 7,150 artifacts have been returned to 26 countries since 2007. If you have information about suspected stolen cultural property, please call the HSI tip line at 1-866-DHS-2-ICE.

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