The members of the Leopoldina are organized in 28 sections that are grouped in four classes.
The era of National Socialism also leaves its mark on the Academy. Members and the leadership of the Academy alike yield to the Nazi regime. After the dictatorship is established in 1933, politics have an increasing influence on the Leopoldina. The relationship between the incumbent Leopoldina President Emil Abderhalden (XX. President, 1932-1950) and the Nazi leadership is rather contradictory and even displays a preemptive obedience at times.
Initially, the Academy tries to ensure that scientific excellence remains its primary concern when admitting new members. However, membership nominations soon have to be submitted to the Nazi authorities, who assess them according to their political vision of a “new Germany”. The lowest point in the previously independent Academy’s history comes when, induced by President Abderhalden, many Jewish scientists are deleted from the list of Leopoldina members. The deletions are carried out in pencil and cancelled after World War II.
From the beginning of the Second World War, the Academy’s development is impaired by the growing isolation of German scientists from their international colleagues. After the war’s end in April 1945, the city of Halle (Saale) is initially occupied by American troops. When the Allied powers rearrange the occupation zones in Germany, Halle (Saale) now falls within the Soviet zone. As a result, the US military administration evacuates many researchers from the university to the American zone beforehand, including some members of the Leopoldina.
Abderhalden is among them. After returning to Switzerland, he formally remains President of the Leopoldina until his death in 1950. Back in Halle (Saale), Vice President Otto Schlüter (XXI. President, 1952-1953) assumes responsibility for the Leopoldina. The outsourced archive and library collections are taken to the Soviet Union by the new occupying power. The ban on all associations severely limits the Academy’s scope of action and puts a halt to new members’ selection.