PYONGYANG, NORTH KOREA — The dress rehearsal for the Korean apocalypse begins at 10 a.m. sharp in Kim Il Sung Square with a terrifying wail of sirens that sends Pyongyang’s citizens fleeing for cover. Fraught-looking women and cloth-capped workers break into a run, and I watch as they race across the broad square, down misty streets, and into the bowels of the subway. Once the square has emptied, the warnings are replaced by the rousing strains of martial music assuring the masses huddled underground of the ultimate victory of the fatherland.

Air-raid drills are a fact of life in Pyongyang, along with scheduled blackouts that plunge this city of two million into an eerie darkness through which even the trams ghost along without lights. This may be the most militarized nation on earth, but people here believe the nuclear threat comes from the outside. "The Americans were the first to threaten a pre-emptive nuclear strike," says my guide, O Jin Myong, as he leads me through the cavernous subway passages decorated with enormous glass chandeliers, Romanesque arches, and huge murals extolling the country’s founder, Kim Il Sung. The platforms, carved more than 100 yards underground, will serve as shelters in an attack, Mr. O tells me. "Here the American bombs can’t get us."

At first, the talk of nuclear bombs and first strikes sounds premature, even paranoid. But during my weeklong visit to the world’s most isolated nation last February, I hear this mantra so many times that it takes on a logic of its own. "Tell the world we are not afraid of nuclear weapons," says an elderly female guide, Ri Ok Hi, after finishing up a tour of a monument to the Workers Party. "We will fight to the death for our leader."

As one of the first Western journalists allowed in since North Korea’s latest nuclear crisis with the United States began last fall, I experience firsthand the paranoia that marks everyday life for North Koreans. For seven days, I am watched, followed, and fed propaganda. From doctors to parsons, everyone I am introduced to — and I have no choice about whom I meet — parrots the same line: hatred of the Americans, matched only by their love of the "Great Leader," Kim Jong Il.

Reverence for the Kim family reaches its zenith at Mangyongdae, birthplace of Kim Il Sung, to which all North Koreans are expected to make a pilgrimage at least once in their lifetimes. Amid perfectly manicured lawns and hedges, lines of youth brigades, women’s groups, and peasants — all dressed in the North Korean equivalent of "Sunday best" — line up to pay homage at the pristine thatched cottages where the "Eternal General" spent his childhood.

I ask the guide, a young woman with excellent English and a petal-pink coat, what she thinks of the founder’s son — the current leader, Kim Jong Il. Taken aback at such an ignorant question, she laughs. "He is my father, also our father," she says, then reverentially points out water jugs from which the elder Kim drank and the mats on which he slept.

A visit to the humble origins of the ruling dynasty is supposed to remind North Koreans how far their nation has progressed under revolutionary leadership. But once out of the showcase gardens and back on the streets of Pyongyang, it is clear that the country, which once styled itself a "workers paradise," is — in material terms at least — regressing.

Only the most privileged five percent of the population — the Workers Party cadres, government apparatchiks, and military brass who run the country — are allowed to live in Pyongyang, which is supposed to be a glittering example of the regime’s centralized planning. Thirty years ago, during North Korea’s economic heyday, that might have been true. It’s still an impressively laid-out city, blending modernist functionality and the green curved roofs of traditional Korean architecture. From every major building, huge images of Kim Il Sung and Kim Jong Il smile down benevolently, and slogans urge the populace to work harder or fight to the death against the American "murderers." While we walk on the eastern bank of the frozen Taedong River, my guides point out the 164-yard-tall Tower of the Juche Idea, the most concrete symbol of the late president Kim Il Sung’s ideological contribution — juche, or self-reliance. But it has been many years since any mighty monuments were built. And even in the capital city, signs of grinding poverty appear to contradict plaudits to the great leader.

At the Grand People’s Study House, North Korea’s national library, two huge reading rooms are dedicated to the works of Kim Jong Il, including treatises on filmmaking, journalism, architecture, agriculture, and, of course, military strategy. Some are so well thumbed that the tattered pages look ready to crumble. The young librarian, Hwang Sun Ryol, insists that her country’s leader wrote 1500 books during his university days. When I doubt that anyone could write a book a day for five years, she does not hesitate: "He is the most outstanding theoretician. No one can match his creativity and enthusiasm." (I thank her and, in the spirit of cultural exchange, donate an anthology of George Orwell’s essays and a video of Monty Python and the Holy Grail.)

The adulation will reach its peak on February 16, the semi-religious celebration of Kim’s birth. Every year, the state-controlled media report miraculous phenomena: concentric rainbows circling the sun, the birth of a new star, and unseasonably warm temperatures at Mount Paektu, said to be the Great Leader’s birthplace (although Western historians say he was actually born in Russia). One year, an albino sea anemone was said to have trapped itself in fishing nets so that it could come ashore to celebrate. I was in Pyongyang the week before the birthday. Posters advertised a huge exhibition of thousands of Kimjongilia (Kim Jong Il flower), the bloom dearest to the heart of every North Korean. The entire nation is said to feel restless and uneasy when Kim is on one of his rare trips outside the country. No matter where he is, at night and early in the morning, Pyongyang’s streets echo with an eerie lullaby, played over loudspeakers, that asks, "Where Are You, Beloved General?"

OUTSIDE THE CAPITAL, international-aid workers say that the cold and hungry people are too concerned about day-to-day survival to bother with ideology. But the state’s propagandists claim the reverse — that the country has been able to endure famine and tension only because of the people’s love for the Great Leader. "Of course, it is a personality cult," said Kim Myong Chol, a former writer for the People’s Daily. "But devotion to our leader is the only thing that keeps us sane. Every morning, people are told to imagine that they are Kim Jong Il. Then, they believe they are part of the most powerful nation on earth."

Devotion to the leader is matched only by hatred of foreigners, especially Americans. The Korean peninsula was once known as the Hermit Kingdom; in some ways, juche is just a new term for historic xenophobia. From kindergarten, North Koreans are taught that the United States is evil and the reason that their country is poor, anxious, and in need of a dictatorship (no one bothers to pretend this is a democracy).

To understand why North Korea feels so threatened, I was taken to the Victorious Fatherland Liberation War Museum, where exhibits purport to show US atrocities during the Korean War, including photographs of alleged massacre victims. "The United States aggressors will never diminish the spirit of our country. We are ready to sacrifice ourselves for the Great Leader Kim Jong Il," says guide Kim Mi Jyong.

Deadly attractive in her military uniform and ruby-red lipstick, Ms. Kim makes an unforgettable impression. I came to think of her as the SMERSH lady because her looks, delivery, and utter conviction would make her the perfect enemy agent in a Bond movie. Our only skirmish, however, is over propaganda. As she taps her pointer on vials of contaminated insects and peculiarly shaped bombs — evidence, she says, that America used biological warfare during the Korean War — I tell her that in the outside world, people believe that her country also possesses biological and chemical weapons. "Is that possible?" I ask.

"No, never. No. No," she replies, shaking her head almost pityingly.

Ms. Kim is missionary in her zeal and utterly charming in the way she tries to open my eyes to the horrors of the American imperialist aggressors. She takes me on a tour featuring the USS Pueblo, an intelligence-gathering ship captured in 1968, and US aircraft shot down by North Korean "ladies" during the war. Conversation returns to the current tensions, and I note that a repeat of the Korean War, in which four million died, would mean terrible suffering for the North Korean people.

She smiles heartbreakingly. "No problem," she replies.

Such messages of suicidal devotion are a staple of the local media. Sitting in a smoky hotel coffee shop, surrounded by aquariums, I read the Pyongyang Times and the comments attributed to Kim Kyong Ho of the Socialist Youth League: "Eight million Korean young people are fully ready to become human bullets and suicide bombs. Even if the enemy is allied to attack us, we will never be frightened. We are sure of our final victory."