Heu-Aktion was the name of an operation to kidnap 40,000 to 50,000 Polish, Belarusian and Ukrainian children by German armed forces for slave labour in Nazi Germany. The term means collective harvesting of hay
Kidnapped children were deported to Nazi Germany and handed over to Organisation Todt and Junkers works. This was with the intention to pressure the adult populations of occupied territories to register as workers in Nazi Reich, and to weaken the “biological strength” of the enemy population of the Soviet Union which Germany invaded.
Originally head of the Reich Ministry for the Occupied Eastern Territories, Alfred Rosenberg proposed to kidnap the youth population between the ages of 15-17, fearing that targeting such young victims would be seen widely as simple abduction, but after actions of 9th Army he consented to kidnapping of children between ages 10 and 14.
The children were transferred to special camps for children called Kindererziehungslager, where Germans studied them for "racial traits", to select children suitable for Germanization. If they were determined to be racially unworthy, their birth certificates were destroyed and names were changed, before being sent to forced labour or to concentration camps, including Auschwitz 
- Forced labor in Germany during World War II
- Generalplan Ost
- Kidnapping of Polish children by Nazi Germany
- Hitlerowski rabunek dzieci polskich (1939-1945)Roman Hrabar 1960 page 99
- Lower, Wendy (2005), Nazi empire-building and the Holocaust in Ukraine, UNC Press Books, p. 117, ISBN 9780807829608
- Lynn H. Nicholas, Cruel World: The Children of Europe in the Nazi Web p 351 ISBN 0-679-77663-X
- TRANSLATION OF DOCUMENT 031-PS
- HITLER'S PLANS FOR EASTERN EUROPE
- Himmlers Raumplanung im Osten: Der Generalplan Ost in Polen 1940-1944 (Stadt, Planung, Geschichte) Bruno Wasser page 221
- Men of 20 July and the War in the Soviet Union Christian Gerlach in War Of Extermination: The German Military In World War II page 139
- "Herrenmensch" und "Bandit" Deutsche Kriegsführung und Besatzungspolitik als Kontext des sowjetischen Partisanenkrieges(1941-44)Timm C. Richter page 106
- NUERNBERG MILITARY TRIBUNAL Volume V · Page 89