WASHINGTON (AP) — The founder of North Korea’s ruling dynasty, an isolationist totalitarian leader named Kim Il Sung, was still building some of the country’s first nuclear facilities when Syd Seiler arrived on the Korean Peninsula as a young U.S. military intelligence officer.

Over the four decades since, Seiler has watched closely as Kim, his son and now his grandson have clung to their nuclear program and developed the potential to lob nuclear warheads at the U.S. and its allies if they choose.

Now Seiler is freshly retired after decades of advising presidents, military commanders and diplomats, making reported secret trips to North Korea and serving as a lead negotiator on talks to contain its nuclear program. And he has a parting message to American leaders: Don’t be discouraged.

North Korea’s fiery rounds of missile test launches are no reason to give up on the international sanctions and pressure, or to simply accept that the ruling Kim family is now a nuclear-armed power, Seiler told The Associated Press this week.

“That’s a failure of deterrence?” he asked, rhetorically. “That’s nonsense. We’re deterring an attack.”

Seiler helped shape the U.S. policy of deterrence, diplomacy and international pressure to deal with the nuclear threat. Following are some of his conclusions, drawing on his decades of experience before retiring this summer as the U.S. national intelligence officer for North Korea:

NORTH KOREAN LOGIC

Seiler sees a strategy and a rhythm to the single-minded nuclear and missile expansion, the rounds of U.S. and South Korean military exercises and North Korean test launches, and the blustery threats, as when the government of Kim Jong Un — grandson of the founding ruler — threatens a “deluge of fire” on neighboring South Korea.

But the Kim family’s worry is not so much about an attack from outside, Seiler argues. He said in sticking to the nuclear program even at the expense of North Korea’s economy, Kim Jong Un has taken a lesson from deposed Romanian dictator Nicolae Ceausescu. A firing squad abruptly ended the communist leader’s rule in 1989 when his people rose up against him.

Having cut North Koreans off from most contact with the outside world, Kim Jong Un, his father and his grandfather before him have seen their regime’s survival as lying in convincing their people the country is a worker’s paradise under threat from the outside world, and only the Kim family and its nuclear weapons can protect them, the former intelligence officer said.

Actions prioritizing the nuclear program over the feeding of your people seem irrational, Seiler said. “But in terms of the logic of North Korea, they make sense.”

RUSSIA TIES

U.S. officials have said Kim Jong Un may travel to Russia this month for a meeting with President Vladimir Putin, who they say is looking to North Korea to supply ammunition for Russia’s war in Ukraine.

Kim “probably sees in this meeting an opportunity to join hands with a like-minded fellow anti-U.S. leader,” Seiler said.

Worrisome possible outcomes include Russia helping North Korea beef up “its pretty antiquated ... museum-ready” conventional forces or its weapons of mass destruction, Seiler said.

“And of course, the worst-case scenario is that Kim Jong Un is watching a leader seeking to ... achieve strategic objectives through the use of force,” Seiler said, referring to Putin’s invasion of Ukraine.

“And suddenly whether Kim, either directly signaled or indirectly signaled by the new relationship with Vladimir Putin, sees a flashing yellow light or green light to engage in similar military actions against” enemy South Korea, he said.

“That would be the worst-of-all fears scenarios,” he said.

But that’s much less likely, he said. “I don’t think what Russia wants to do is to seek a relationship with North Korea in any way that significantly leads to instability in the region.”

THREAT TO SOUTH KOREA

Even this year, one U.S. intelligence assessment has been that Kim Jong Un would continue to be a bellicose neighbor for South Korea and an unpleasant member of the global community — but was unlikely to actually wage nuclear war at least through 2030.

But Seiler and others see growing reasons to worry now about what Kim may have planned for South Korea, its democratically governed and U.S.-allied neighbor.

As Kim expands and improves his nuclear arsenal beyond what he would need for deterrence, he has sharpened his threats toward the south in the past 1 1/2 years while honing ballistic missiles capable of reaching the U.S., South Korea’s protector, Seiler noted.

“North Korea was clearly developing capabilities that would enhance its position vis-à-vis South Korea. And so going forward, this is where the room for concern is,” Seiler said.

Coupled with growing domestic debate in South Korea about how much the country should rely on the United States’ protection, there’s “kind of an awakening of a North Korea threat that, frankly, we should have caught on to a couple of decades ago,” he said.

Denial or wishful thinking may have led some in the West to overlook the implications of the growing threat for a time, he said, although the intelligence community was well aware.

Meanwhile, Putin is battling in Ukraine to reclaim what he maintains is Russia’s historical territory, and the U.S. and its allies are paying growing attention to China’s stated openness to reclaiming Taiwan by force if need be.

It’s all “helped create an environment where this issue of what Kim Jong Un might choose to do in the use of force domain, backed by his nuclear weapons, is a greater subject of debate than it was even a year ago,” Seiler noted.

How strong is that risk right now?

“Well, I think right now Kim is deterred,” Seiler said.

‘I WAS BROUGHT TO TEARS’

Among his experiences in North Korea that stood out, Seiler pointed to watching a landmark 1983 Korean television show. Unscripted, the show turned into an emotional, marathon, 453-hour live broadcast that reunited Korean families divided under Japanese colonization or during World War II and the Korean War.

For Koreans, the broadcast laid bare the heartache of separated families in the Cold War. It led to what would be sporadic and brief North-South reunions across the rigidly divided Korean Peninsula.

“‘I grew up here. I lost my sister there. My little sister had a birthmark there,’'' Seiler said, recounting those who called in to the show. ”And someone would call in and say, ‘Hey, are you so-and-so?”’

“I was brought to tears by it,” Seiler said. For an outsider, it made clear the lasting human costs of the barriers that the North had erected against the South.

“But it’s also a reminder,” Seiler said. “We can never let the humanitarian dimensions of this issue fall off the table.”