Research conducted by Perplexity AI using the following sources:

• Trump announces tariffs on 8 NATO allies in latest push to acquire Greenland
• Trump announces tariffs on NATO allies for opposing US control of Greenland
• Trump and the Transatlantic Alliance: Greenland, Tariffs, and NATO Under Strain
• America's NATO allies erupt in tariff fury: read their rebuke of Trump
• Trump Retracts NATO Tariffs - AAEI