"Fire & Fury"

The history of bombastic empty threats is a rich one.  Mussolini was an absolute master of the art, he referred to the Mediterranean as "Our Sea", threated to invade islands already under Italian Control & his territorial demands at the armistice talks with France in 1940 are as funny as any work by P.G. Wodehouse.
Achmed Sukarno (once the top swank in Indonesia in the 1960's) wanted to rename the Indian Ocean "The Indonesian Ocean" as soon as his poverty wracked nation Got The Bomb of Course.
The late Gamal Nasser used to threaten to push Israel "into the sea" on a daily and sometimes hourly basis, The Late Colonel Ghadaffi used to howl imprecations at the US Seventh Fleet....its all very bloodcurdly and usually impotent.
Because these are threats that are uttered largely for domestic consumption or to rhetorically deter certain international threats, they are the recourse of international actors with limited resources.  Komrade Kim v.3 in Pyongyang makes all sorts of crazy threats to forestall the very real possibility of a US Backed Invasion while spending scarce resources to a crude nuclear deterrent he thinks will somehow keep the wolf from his door.
Thats the main reason he is building those nukes to keep us out, he can't really do much more with them at all given North Korea's small size and stagnant economy.
In other words to quote my late father "threats are the lexicon of weaklings", and its worth noticing that Asia's top threatener, Komrade Kim hasn't yet made good on a single one of his voluminous of international carnage.  Thus for Donald Trump to get down to Kim's Level and counter threaten all sorts of merciless mayhem, it isn't so much a sharp rebuke as a confession of a similar degree of weakness.
But remember, the weak make bad decisions on the fly so all this palaver of mine can go up in smoke pretty instantly.