Given Trump's ridiculous trade war, where is the Pentagon going to get its samarium, tungsten, gadolinium, terbium, dysprosium, yttrium etc

The ores containing these rare earth elements are not found in significant deposits in the US. They are found in low concentrations in Canada, higher in South Africa and Australia,  but mostly in China. China isn't hitting the US with tariffs - they're stopping export altogether. These rare elements are VITAL to the US defense industry, as well as electric motors, aircraft engines etc.
Unless the US can source them elsewhere (they can't, nobody else has got any), there will be no more semiconductors so there goes your electronics industry. Airbus already produces better airplanes than Boeing, but without yttrium Boeing will be forced to cease production altogether. Elon can't build his Teslas without neodymium and dysprosium. And no more stealth bombers or ammunition without tungsten.

Supply chains. His Royal Orangeness has shattered them. Defend THAT, MAGAts.