Here's what you need to know to get up to speed.
North Korea is a state with nuclear weapons and all the talk of war and is not going to undo that fact. Russian Federation and China have opposed doing anything that could lead to the collapse of Kim's regime. A new war in Korea not only risks nuclear confrontation, it would be deadly with only the use of conventional forces.
The new satellite images of the Punggye-ri nuclear test site were taken Monday, the day after the nuclear detonation.
August's sanctions did not target North Korea's oil imports, vital for its economy to function, or completely ban North Korea exporting labor, with remittances sent home from North Korean workers vital for funding its nuclear program.
"We should not give in to emotions and push Pyongyang into a corner", Putin said in a news conference after meeting with Moon.
US Secretary of Defense Jim Mattis in a phone conversation with Japanese Minister of Defense Itsunori Onodera reaffirmed the intention of the United States to help Japan strengthen its ballistic missile defense. President Donald Trump has said all options are on the table and told British Prime Minister Theresa May on Tuesday that "now is not the time to talk to North Korea", according to a White House readout. We'll see whether or not he can do it.
Seoul's Foreign Ministry spokesman Cho June-hyuck said Thursday that the message posted on the website of the South Korean Embassy in Beijing was aimed at protecting the safety of South Koreans in China. Seoul also said the United States was preparing to bolster its military presence amid concerns the North appears to be preparing to launch more missiles in the wake of Sunday's test.
And while the United States possesses overwhelming firepower compared to North Korea, any American strike on North Korea would likely expose neighbors South Korea and Japan to devastating casualties, analysts say.
One option of dealing with a rogue state such as North Korea is military action.
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Sanctions so far appear to have done little to stop North Korea from boosting its nuclear and missile capacity as it faces off with Trump, who has vowed to stop Pyongyang from being able to hit the US mainland with a nuclear weapon.
Over the last few years, the United Nations have issued increasingly tougher sanctions of North Korea, and are now considering taking these steps further.
US Treasury Secretary Steve Mnuchin said he had an executive order ready for Trump to sign that would impose sanctions on any country that trades with Pyongyang if the United Nations does not put additional sanctions on North Korea. We are fulfilling our due worldwide obligations, at the same time, we will continue to approach the relevant issue with the principle of helping realize the denuclearization of the Korean Peninsula and uphold peace and stability there.
Since 2006, the Security Council has unanimously adopted eight resolutions ratcheting up sanctions on North Korea over its ballistic missile and nuclear programs.
What to do about North Korea? On Wednesday, he appeared to rule out negotiations, saying on Twitter that "talking is not the answer". "If we fail to stop North Korea's provocations now, it could sink into an uncontrollable situation", Moon said in remarks before the meeting.
She said the United States does not want war but will defend itself and allies when North Korea is issuing threats with missiles pointed at US territories.
"It is a choice between bad and worse, and in this case all alternatives to the freeze are indeed, worse", said Lankov.
The Moon administration faces the prospects of increased US tariffs at the same time it is experiencing informal sanctions from China for deploying the American THAAD missile defense system. Plus, as experts have told ThinkProgress, China has no interest in regime change in North Korea.
Also on Sunday, Trump mentioned the possibility of "stopping all trade with any country doing business with North Korea".