The humanity of this action in a time where pretty much no other nations (at least I cannot think of a single other one atm) let their actions be guided by humanity will forever be the most impressive thing about this.
During WWII Denmark was occupied by Nazi Germany but was a “model protectorate” and retained much of their freedom.
However, in 1943 Hitler ordered the arrest and deportation of all Jews in Denmark. As word of the orders spread, Jewish individuals were warned to go into hiding, and the majority of them did so. But it was known that they could not stay in hiding forever without being discovered. Plans were made to smuggle as many of the Jewish population as possible to Sweden. On October 2, 1943 Swedish radio broadcast that they were ready to offer asylum to Danish refugees.
In fishing boats and other small craft over 7000 Jews were smuggled out over the Oresund to Sweden in the following weeks.
Only 5% of the Jewish population in Denmark was deported to concentration camps. The Danish people constantly demanded information on the whereabouts of these individuals, which may have saved them from being transferred to death camps. As a result of these efforts 99% of Danish Jews survived the holocaust.