I asked ai, so take this answer for what it is, but it makes sense to me.

National security is the primary reason cited by President Donald Trump for wanting control of Greenland.

He has stated that the U.S. needs Greenland "from the standpoint of national security," arguing that the island is strategically vital due to its location between North America and Russia, and its proximity to emerging Arctic shipping routes and missile trajectories.

Strategic military positioning plays a key role. Greenland sits astride the GIUK Gap, a critical naval chokepoint linking the Arctic and Atlantic Oceans, and provides early warning capabilities against potential missile threats from Russia or China. The U.S. already operates the Pituffik Space Base (formerly Thule Air Base) in northwest Greenland, which monitors missile activity and supports space surveillance.

Concerns about rival powers are central to Trump’s argument. The White House claims that Russia and China are increasing their presence in the Arctic, with Trump warning that if the U.S. does not act, one of these nations could take control of Greenland. This rationale follows a broader push for Arctic dominance amid melting ice and growing geopolitical competition.

Economic and resource interests are also widely believed to be a factor, despite Trump downplaying them. Greenland holds vast untapped reserves of rare earth elements, critical minerals, oil, and gas—resources essential for clean energy technologies and defense systems. Some analysts and officials, including former national security adviser Mike Waltz, have suggested that access to these minerals is a major driver behind the administration’s interest.