As Donald Trump prepares to take office as president again, a huge controversy is brewing between him and UK Prime Minister Sir Keir Starmer. It all revolves around a secretive UK-US military deal about the Chagos Islands, a small but strategically important group of islands in the Indian Ocean.

At the center of this disagreement is the US military base on the island of Diego Garcia, which plays a key role in global security. For years, the UK has controlled the Chagos Islands, but a rec...