Even for a nation that has perfected the provocative, North Korean leader Kim Jong Un’s declaration that he would abandon the existential goal of reconciling with rival South Korea was a shock. But a closer look shows it is the almost inevitable culmination of years of building tension.

World powers will now be closely watching to see how one of Mr. Kim’s biggest foreign policy declarations since he took power in 2011 plays out as he works to gain leverage in a region that holds both promise and danger for his small, impoverished, nuclear-armed nation.

The bombshell came at a rubber-stamp parliament meeting in early January, where Mr. Kim called for rewriting North Korea’s constitution to eliminate the idea of a peaceful unification between the war-divided countries and to cement the South as an “invariable principal enemy.”

It is the clearest sign yet of how far inter-Korean relations have fallen since February 2019, when Mr. Kim’s nuclear diplomacy with former U.S. President Donald Trump imploded in Hanoi, Vietnam. Talks there fell apart with no joint agreement. The animosity that followed that highly public setback has been accompanied by an accelerated and unprecedented expansion of Mr. Kim’s nuclear arsenal and by repeated threats of nuclear war against Washington and Seoul.

Mr. Kim, who during the recent Supreme People’s Assembly meeting described South Korea as “top-class stooges” of America, may be attempting to diminish South Korea’s regional power while moving toward direct U.S.-North Korean nuclear talks.

Mr. Kim’s new approach to the South comes as he tries to break out of diplomatic isolation and strengthen his footing regionally. He is playing off deepening U.S. tensions with Moscow and Beijing over Russia’s war in Ukraine and China’s assertive foreign policy.

North Korea’s recent efforts to boost ties with Russia and China and join a united front against Washington in what Mr. Kim calls a “new Cold War” were highlighted by his September visit to Russia for a summit with Russian President Vladimir Putin.

North Korea has been recalibrating its regional approach since the collapse of the 2019 Hanoi summit, said Ankit Panda, an expert with the Carnegie Endowment for International Peace.

“But now, with advanced nuclear and missile capabilities and the support of Russia and China, Kim feels confident enough to make these changes, which amount to his most consequential proclamations on external affairs since taking power in North Korea,” Mr. Panda said.

From Partners to Adversaries

North Korea no longer sees Seoul as a useful middleman to extract concessions from Washington. Instead, its rival is now seen as an obstacle to the North’s efforts to carve out a more assertive presence in global affairs, said Hong Min, an analyst at South Korea’s Institute for National Unification.

Pyongyang has viciously criticized South Korea’s conservative President Yoon Suk Yeol, who, since taking office in 2022, has expanded military cooperation with Washington and Tokyo while seeking stronger U.S. assurances that it would swiftly and decisively use its nuclear capabilities to defend its ally in the event of a North Korean nuclear attack.

In eliminating the idea of a shared sense of statehood between the Koreas, Mr. Kim could be reinforcing North Korea’s older approach of ignoring South Korea and attempting direct dealings with Washington. The old reasoning in Pyongyang, according to Mr. Hong, was that the South was not a direct party to the armistice that ended the bloodshed of the 1950-53 Korean War. That ceasefire was signed between the U.S.-led UN Command, North Korea and China, which sent troops to fight for the North.

Declaring the South as a permanent adversary, not as a potential partner for reconciliation, could also be aimed at improving the credibility of Mr. Kim’s escalatory nuclear doctrine, which authorizes the military to launch preemptive nuclear attacks against adversaries if the leadership is under threat, Mr. Hong said.

An intensifying campaign to eliminate South Korean cultural influences and to reinforce the North’s separate identity may be aimed at strengthening the Kim family’s dynastic rule.

At the assembly, Mr. Kim ordered his country to remove past symbols of inter-Korean reconciliation, including a cross-border railway section and a unification monument in Pyongyang he described as an “eyesore,” and to “completely eliminate such concepts as ‘reunification,’ ‘reconciliation’ and ‘fellow countrymen’ from the national history of our republic.”

“North Korea is aiming to destroy the illusions of unification, inter-Korean exchanges and cooperation that remain in the minds of its people,” said Lim Eul-chul, a professor at Seoul’s Kyungnam University’s Institute for Far Eastern Studies.

This is the reverse of Mr. Kim’s approach in 2018 when he initiated diplomacy with South Korea’s former liberal president, Moon Jae-in. He later used Seoul as a bridge to engage with Mr. Trump, part of an ambitious effort to leverage his nukes for badly needed economic benefits.

After the failure in Hanoi, North Korea halted all cooperation with the South and blew up an empty inter-Korean liaison office in 2020 to display its displeasure toward Seoul.

Long-Term Focus

In recent months, Mr. Kim has used Russia’s war on Ukraine as a distraction to dial up weapons tests to a record pace. The alignment between North Korea and Russia has raised worries about arms cooperation, in which the North apparently provides Russia with artillery shells and missiles to help prolong its warfighting capabilities, possibly in exchange for economic and military assistance.

Both Moscow and Pyongyang have denied U.S. and South Korean accusations of North Korean arms transfers to Russia.

“Russia is in need of North Korean weapons, and that has naturally boosted the North’s munitions industry and injected some vitality into its economy, and in return, North Korea [likely] receives energy, food and technology assistance,” said Koh Yu-hwan, a scholar at Seoul’s Dongguk University and former president of the Institute of National Unification.

Mr. Kim’s long-term focus is to force Washington into accepting the idea of North Korea as a nuclear power, and he may be intent on driving up tensions in a U.S. election year with a view to eventual talks with whoever wins the November election, according to Park Won Gon, a professor at Seoul’s Ewha University.

North Korea for years has mastered the art of manufacturing tensions with weapons demonstrations and threats before eventually offering negotiations aimed at extracting concessions.

Mr. Yoon’s government also faces crucial parliamentary elections in April.

While some analysts argue that Mr. Kim may have made a strategic decision to wage war with the South, others downplay the possibility.

“The risks of an inter-Korean clash cannot be ruled out, but North Korea may choose to test South Korea’s thresholds below the threshold of all-out conflict,” Mr. Panda said. “Political moments in both South Korea and the United States also make this an appealing approach for Kim.”

This article contains information from The Associated Press.