Why does Trump want Greenland to be part of the U.S.?

Why does the United States want control of Greenland? President Trump has made it clear that he thinks the U.S. needs to control the Arctic island to ensure the security of America and its NATO allies, a point those allies — and Greenland — vehemently disagree with.

But there's more at play here, including a valuable shipping route and access to mineral resources.

Here's what interests the U.S. about the semi-autonomous Danish territory...