Every year since 1947 the city of Oslo has given a huge christmas tree to the people of London. The reason for this tradition is Norway wanting to thank the english people for the help they provided during the German occupation of Norway between 1940 and 1945. The tree is decorated in a traditional Norwegian manner with more than 500 light bulbs.
Here is an example of one of their actions.
The story in the link above is about two british RAF pilots who take part in the bombing of Porsgrunn harbour. Their plane is shot down and they crash into a lake. They are saved by two Norwegian Farmers who take care of them.
Later the Germans find them and kill the Norwegians before the pilots are taken prisoners. This operation was preformed in April 1945 and not long after the pilots where arrested the war ended and thy were set free.