Who is King Christian X?

Lois Lowry's novel Number the Stars is set in Nazi-occupied Denmark in the year 1943. Annemarie Johansen is best friends with a girl her age named Ellen Rosen, who is Jewish and therefore in danger of being taken and killed by Nazi soldiers. With the help of the Johansen family, Ellen and her family are eventually safely smuggled to Sweden, which was able to remain a neutral country during World War II. 
King Christian X is the King of Denmark, and Annemarie remembers the times when he used to ride through the streets of Copenhagen. In the timeline of this story, King Christian was forced to surrender to Germany three years before, because Denmark was not strong enough to defend itself against Nazi military forces. It is clear that the king is very well loved and respected by the people of Denmark, and he supports all those who fight against the Nazi regime.