Donald Trump says the U.S. needs control of Greenland and the Panama Canal "for national security." Here's why both places are so important.

The president has repeatedly discussed his desire to "retake" the Panama Canal and take possession of Greenland.

President-elect Donald Trump wouldn't rule out military or economic coercion, saying the U.S. needs to stop China. Also a factor: climate change.

Authorities of Panama and Greenland have repeatedly said they won't hand over any territory to Trump, with Panama's president declaring that the canal "is going to stay in our hands forever," and Denmark's prime minister insisting "Greenland is not for sale."

In his speech, Trump vowed to lead a government that "expands our territory," referencing his ambitions to acquire Greenland from Denmark and reclaim U.S. control of the Panama Canal. However, the path to achieving these goals remains uncertain, as he is likely to face resistance both domestically and internationally.

There are other climate-related reasons for Mr. Trump to be interested in Canada and Greenland as they gain grain-growing land while we lose a chunk of ours to increasing temperatures, but it sounds just now as if Mr. Trump has shipping and the related matter of projecting naval power in mind.