U.S. president’s swipe at NATO troops in Afghanistan mark latest challenge to alliance.

President Trump suggested the U.S. should have tested NATO’s commitment by invoking Article 5 in response to the southern border crisis.

The French troops will join those from Germany, Norway and other countries.

The president's push to gain control of Greenland, a Danish territory, has created anxiety about the future of the alliance throughout Europe.

The president's goal of annexing the Danish territory has already created cracks in the mutual trust that holds NATO together.

Perhaps at no other time in the North Atlantic Treaty Organization’s 75-plus year history has the alliance’s future faced greater uncertainty. President Donald Trump, a longtime NATO critic, has made the annexation of Greenland a key second-term objective,

An estimated 3,500 soldiers from NATO countries died in Afghanistan. The United States suffered the most losses in absolute terms: Nearly 2,500 U.S. service members were killed in the 20-year war. But per capita, Denmark suffered even more severe losses, burying 43 soldiers in a population, at the time, of about 5.5 million.