

Knight's Cross with Oak Leaves
The Knight's Cross of the Iron Cross with Oak Leaves (Ritterkreuz des Eisernen Kreuzes mit Eichenlaub) was instituted on 3. June 1940. Before the introduction of the Oak Leaves only 124 members of the Wehrmacht had received the Knight's Cross. Prior to Case Yellow (Fall Gelb), the attack on the Netherlands, Belgium and France, just 52 Knight's Crosses had been awarded. In May 1940 the number of presentations peaked. The timing for the introduction of the Oak Leaves is closely linked to Case Red (Fall Rot), the second and decisive phase of the Battle of France.
Like the Knight's Cross to which it was added, the Oak Leaves clasp could be awarded for leadership, distinguished service or personal gallantry. The Oak Leaves, just like the 1813 Iron Cross and Grand Cross of the Iron Cross, was not a National Socialist invention. They originally appeared in conjunction with the Golden Oak Leaves of the Order of the Red Eagle, which was the second highest Prussian order after the Order of the Black Eagle. The king also awarded the Oak Leaves together with the Pour le Mérite since 9. October 1813 for gallantry.
https://en.wikipedia.org/wiki/Knight%27s_Cross_of_the_Iron_Cross#Knight's_Cross_with_Oak_Leaves
863 officially bestowed recipients