Tensions between North and South Korea escalated further on Wednesday as Kim Yo-jong, sister of North Korean dictator Kim Jong-un, launched a torrent of insults at leftist South Korean President Moon Jae-in.

The Moon administration, which has previously been conciliatory toward the North and touted diplomatic openings across the border as its highest achievements, responded by calling her remarks “unprecedentedly senseless” and “very rude.”

Kim, who appears to have taken point in North Korea’s increasingly belligerent communication with the South, slammed Moon as an “impudent man” full of “honeyed words.” She described Moon’s recent public remarks as “sickening.”

The subject of Kim’s tirade, which frequently verged into sputtering incoherence, was the anti-regime leaflets spread in North Korea by defectors living in the South. North Korea became suddenly and violently enraged by these leaflets over the past week, expressing its ire on Tuesday by blowing up the inter-Korea liaison office in Kaesong, a city near the Demilitarized Zone (DMZ). According to some North Korean sources, the destruction of the four-story building was ordered by Kim Yo-jong.

In her tirade against Moon, Kim used the standard regime parlance of “human scum” to describe the leaflet-spreading defectors and, in very colorful language, castigated the South Korean president for not doing enough to stop them. A major point she hit several times during her outburst is that the leaflets dispersed by the defectors are supposedly insulting to her brother, regarded as unassailable and indeed semi-divine under North Korean state mythology.

“They dared defame the dignity of our supreme leadership, our Chairman whom we hold most sacred as the central core, and mocked at all our people at the same time,” she raged.

“Whenever [Moon] makes public appearances, he lets out childish and hope-filled dreamy rhetoric and tries to look big, just and principled just like an apostle of peace. It was so regretful for me to see his disgusting behavior alone. So I decided to prepare a bomb of words to let it be known to our people,” Kim said.

Moon’s office, the presidential Blue House (or Cheong Wa Dae in Korean), condemned Kim Yo-jong for her “rude and senseless” attacks and said it would not “tolerate any more of North Korea’s indiscreet rhetoric and actions.”

Kim Yo-Jong’s new role as fire-breathing critic of Moon Jae-in was exceptionally disappointing for Moon’s supporters because she was formerly seen as a key player in North Korea’s diplomatic opening to the South, and supposedly had developed a decent personal relationship with Moon. Kim became something of a celebrity to left-wing American media organizations for making rude faces at U.S. Vice President Mike Pence during the Pyeongchang Winter Olympics in 2018.

A Cheong Wa Dae official said Pyongyang will be held responsible for “all consequences” of its belligerence. 

The North Korean army retorted that it stands ready to “provide a sure military guarantee for all external and internal measures to be taken by the [Communist] Party and the government.”

North Korean officials said they are deploying troops into former areas of civilian cooperation, restoring guard posts in the DMZ that were removed during the past three years of diplomatic progress, and moving artillery units back into position. In an added jab at Seoul, the North Korean military said it would begin dropping its own propaganda leaflets over South Korean territory.

Despite Kim’s rantings about the leaflet-spreading defectors, the South Korean government actually has tried to stop them, drawing condemnations from free-speech advocates such as Human Rights Watch (HRW). 

HRW denounced efforts by South Korean law enforcement to shut down the leaflet campaign as an offense against freedom of speech and a lamentable example of “kowtowing” to pressure from Pyongyang.

“Instead of proposing a blanket ban on sending balloons with messages and materials to the North, President Moon should publicly demand that North Korea respect freedom of expression and stop censoring what North Koreans can see,” HRW’s deputy Asia director Phil Robertson said last week.

“President Moon and his colleagues fought for much of their lives and careers to protect human rights in South Korea. It is shameful how President Moon and his government are totally unwilling to stand up for the rights of North Koreans,” Robertson added.

Predicting the actions of the secretive and paranoid North Korean regime is always difficult, but some analysts believe the sudden fury over defector leaflets is largely a theatrical performance intended to force more concessions out of South Korea and restart diplomatic engagement on Pyongyang’s terms. 

Some also see it as a power play intended to boost Kim Yo-jong’s stature in the North Korean regime, giving her the boost she might need to shatter the glass ceiling and become a top figure, or even dictator, of the male-dominated system.  

“What we see right now is North Korea working out a contingency succession plan in case Kim Jong-un’s health goes bad,” analyst Yoo Dong-ryul of the Korea Institute for Liberal Democracy in Seoul told the New York Times on Wednesday.

A third possibility is that North Korea’s patrons in China want to destabilize Asia at a time of rising tensions with the United States, India, and everyone around the world who holds Beijing responsible for the coronavirus pandemic and has decided Pyongyang should once again become the feral attack dog that only a firm Chinese hand can hold at bay.

In the best-case scenario, China wants Kim Yo-jong playing the heavy in a “good cop, bad cop” routine with her brother to keep the West preoccupied. In the worst interpretation, China is close to deciding that its dreams of more-or-less peacefully dominating Asia have been foreclosed by the coronavirus, so a war on the Korean peninsula that weakens South Korea, Japan, and American forces might be in its interests, no matter the risks to Chinese citizens living near the North Korean border.