Twenty years ago, I spent a couple of weeks in Afghanistan with Britain’s Royal Marines. Operating largely under British command in Helmand was a Danish contingent made up largely of special forces. The Marines had nothing but praise for their Danish allies, who were in some of the toughest firefights and who suffered the highest per capita rate of fatalities after the United States.

Why were they there at all? What made Denmark send 750 men to those remote mountains? There was only one explanation. Danes had felt the atrocity of 9/11 as an attack on the entire West. When the U.S. called for help, the no-nonsense Norsemen did not hesitate.