Many observers feared North Korea would carry out its sixth nuclear test , or that the USS Carl Vinson and its escorts -- which Pyongyang at the time thought were just off the coast of North Korea -- would attack.

Very few people outside the US administration knew the carrier group was in fact some 3,500 miles away from the Korean Peninsula

Both North Korea and the United States warned of devastating consequences if the other made a move. Only a small miscalculation in Pyongyang, Washington or Beijing might have sent the situation spiraling into violence.

But in the end none of that happened. Instead, the next day, North Korea tried and failed to launch a medium-range missile , to which neither the United States nor China responded. We got through yet another North Korean crisis.

In my opinion, the most plausible explanation for this is that North Korea blinked. Although it is possible the extensive preparations around its nuclear test site were intended only to wind up the international community, it seems more likely that the North Koreans did indeed plan a nuclear test Saturday but desisted, probably because they assessed the risks of serious retaliation were too great.

The US carrier group it thought was near Korea and China's threat on April 12 to support UN sanctions, including cutting off North Korea's oil supply -- which would have quickly brought its fragile economy to a halt -- probably weighed heavily on Pyongyang as well.

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Perhaps the North Koreans calculated (rightly, it seems) that either a nuclear test or a test of an intercontinental ballistic missile -- a long-range missile of the kind they would need to carry a nuclear warhead to the continental United States -- was too dangerous. Instead, launching a medium-range missile would allow them to deny they were buckling under foreign pressure while not triggering a vigorous international reaction. The fact it failed doubtless also softened responses.

If this analysis is right, then the United States has, for now at least, succeeded in its long-term goal of halting the development of North Korea's nuclear weapons and missiles.

To perfect these weapons, North Korea needs to test them, and if it dares not do so for fear of the consequences, then its program is effectively frozen. The deputy foreign minister's assertion that North Korea will continue testing missiles "on a weekly, monthly and yearly basis" should be taken with large pinches of salt. Further launches of medium-range missiles such as that on Sunday will not greatly help North Korea to develop an effective ICBM.

Early in his presidency, Donald Trump commissioned a review of policy on North Korea. Leaks being circulated around the diplomatic community suggest its broad recommendations are that, rather than pursue negotiations (the North Koreans have said they will never negotiate away their nuclear weapons), the United States should increase pressure on Pyongyang to abandon its nuclear program.

The deployment of the USS Carl Vinson, due to reach the Korean Peninsula later this month, is likely to be part of this new policy, as are the renewed efforts to coordinate action with China to which US national security adviser H.R. McMaster referred on Sunday . Perhaps the Chinese threat to support cutting off oil supplies is an early fruit of this new dialogue.

This is not an entirely new departure. Previous presidents have tried to deal with North Korea through sanctions, and President Bill Clinton contemplated a military strike. But we have not previously seen such threats of military action (backed by examples in Syria and Afghanistan) combined with energetic consultations with China and the consequent threat of much heavier sanctions.

These are very early days, and the policy has serious risks -- will Pyongyang, for example, respond to economic pressure with military adventures? But so far it at least seems to have put Pyongyang on the back foot.