It seems Trumps warnings have worked, for now... Great news! What should be the next step? What do you do now to prevent this from happening again in a few months/years? NK won't stop developing their nukes.
I wouldn't be so quick to credit Trump for defusing the crisis.
Or you might be right, and he & James Mattis may have scared NK into backing off. Maybe the NKs blinked first, as the Soviets did in JFK's era?
It's also possible that the North Koreans have run into some engineering challenges. Testing missiles in the Pacific Ocean, in a specific area only 40km from a populated island, with a narrow deadline? I was really surprised that they were ready to guarantee in advance that they could test near Guam. They have to (try to) secretly transport the missiles over mountainous roads, set up a platform, move the missile into place, fuel it, etc. Their systems are under cyber attacks as they do this. What if they miss the target ring around Guam, and hit the island accidentally? Imagine if they hit a Chinese ship! When testing in the East Sea (of Japan), they can patrol the target area to make sure it's relatively clear. These are unarmed missiles, of course, but the political damage and the loss of face...
We'll never know which happened, until perhaps the Kim regime eventually dies and disappears.
To answer your question, DH, there's absolutely nothing to prevent this from happening in a few weeks or months. NK
will keep making threats. They will keep taking lives of SK sailors, civilians, etc. They'll say and do outrageous things, because this is how they force their Chinese patrons to supply them with oil & food. And they will do only small, occasional things, since they don't really want war with the USA. Just the constant threat of war.
Someone mentioned dropping leaflets. Yes, there are various methods of sharing different points of view with North Korean citizens. Helium balloons with USB drives. Loudspeakers. Smuggling Bibles in. Giant signs. Giant Christmas trees. Some ways are more effective than others. It's hard to know, though, how many "true believers" there really are. How many NKs really believe that KJU has no anus -- never has to use the RR? They're frightened out of their lives, for fear of being ratted out by neighbors or even family members, lest they allow a newspaper article with photos of the Dear Leader & Great Leader to fall to the floor. That's one of MANY no-no's that can land them in a gulag-style prison, where zombie-like prisoners will literally search through the feces of an animal to find an undigested kernel of corn. In his presence, they generally cry, but how much of this is because they honestly worship the dude, and how much due to fear?
These poor souls need our prayers, and no matter what your political feelings are, so do the leaders of all nations with WMDs. So, yes, pray for Kim Jong Un, Bashar al-Assad, Mamnoon Hussain (Pakistan), and so on, and for the military leaders who advise them. May they find the way of peace. And may Pres. Donald Trump, Sec. Rex Tillerson and Sec. James Mattis do so, too.