SEOUL: The path to Pyongyang's latest nuclear test followed a textbook North Korean strategy: escalating provocations accompanied by furious denunciations of annual South Korea-US military exercises.
In the 12 days since Washington praised Pyongyang's "restraint" and held out the prospect of early talks, the North has fired three short-range missiles, sent another one soaring over Japan and detonated what appears to be a full-fledged thermonuclear device.
"The hydrogen bomb test was a perfect success," an announcer on state TV claimed after Sunday's test.
While some western media delight in portraying the North Korean regime as irrational -- or even unbalanced -- experts say it demonstrates an extremely refined ability in calibrating and timing its actions to maximise their impact.
The fuse for Sunday's detonation was lit with the test in July of two intercontinental ballistic missiles (ICBM) that appeared to bring much of the US within range.
That sparked a fierce warning by President Donald Trump that Washington could rain "fire and fury" on the North, while Pyongyang unveiled a plan to fire a salvo of missiles towards the US territory of Guam.
North Korean leader Kim Jong-Un later said he was putting the plan on hold, but warned he could still give the order depending on Washington's next move.
The final countdown then began on August 21 when the United States and South Korea kicked off an annual military exercise called "Ulchi Freedom Guardian" involving tens of thousands of troops.
The North, which sees such war games as rehearsals for invasion, said the US would be "pouring gasoline on fire" by going ahead with the drill.
Its initial military response came on August 26 with the relatively innocuous launch of three short-range ballistic missiles.
That was followed three days later by the far more provocative launch of an intermediate-range missile over Japan -- a move that triggered consternation in Tokyo and the wider region.
Sunday's H-bomb test was flagged just hours before by the release in the North's state media of photos of Kim inspecting a "thermonuclear weapon" capable of being mounted on an ICBM.
More than 60 years after the end of the Korean War, the impoverished North uses the perceived threat of US invasion to justify its nuclear weapons programme.
The annual military exercises in the South always lead to a sharp rise in tensions, and the North's fifth nuclear test on September 9 last year also followed the annual war games.
China, under fire from Trump for failing to restrain its neighbour and ally, has pushed for a suspension of the North's nuclear and missile tests in exchange for a halt to the drills -- a quid pro quo firmly rejected by Seoul and Washington.
If the North's playbook for the latest test is familiar, there is a wild card in the form of the new occupant of the White House.
While his advisers stress diplomacy, President Trump has repeatedly raised the option of military measures to shut down the North's nuclear and missile programmes.