Why wouldn't that be announced in advance? It'll be detectable internationally as soon as it happens.

If true they would have told the Russians and the Chinese and yes everybody will know after the fact. But for various reasons they might not want to disclose ahead of time in case Trump gets talked out of it or they realize they're not ready or various other reasons (perhaps the Energy Dept. doesn't actually want to do it but they're going forward step by step hoping it gets halted).

	▲	mikkupikku 8 hours ago \| parent [-]
		If they already know, complaining about it in advance will soften the public shock when it happens, which is probably not what Russia and China want. They'd prefer that the rest of the world be maximally shocked and outraged by such a transgression of international norms.