Complex sentence: A large archive of his photographs was seized by the United States government during the Allied occupation of Germany, and now, held by the National Archives and Records Administration, comprises one of the most important sources of images for scholars of the Third Reich.
Split into simpler sentences: A large archive of his photographs was seized by the United States government during the Allied occupation of Germany. These are now held by the National Archives and Records Administration and comprise an important source of images for scholars of the Third Reich.