Military officers visit the birthplace of North Korean founder Kim Il Sung on April 14, a day before the 105th anniversary of his birth. (Damir Sagolj/Reuters).

Expectations are running high that North Korea will do something provocative in the next few days — even if it’s just a military parade where they show off mock-ups of missiles — to mark the biggest day of the year on the North Korean calendar.

April 15 is officially known in North Korea as “The Day of the Sun” and marks the birthday of the founder of North Korea, Kim Il Sung, in 1912. (Incidentally, he was born on the same day that the Titanic sank.) It’s called that because Il Sung means “to realize the sun” in Korean — although this is not the founder’s real name but a nom de guerre.

Here’s a brief rundown on why Kim Il Sung — who’s officially “Eternal President,” even 23 years after his death — remains so important in North Korea.

Some background

Kim Il Sung was an anti-Japanese guerrilla during the first half of the 20th century, when Korea was one country and occupied by the Japanese. At the end of World War II, the peninsula was divided along the 38th parallel, with the Soviet Union overseeing the northern half and the United States taking the southern half.

Stalin installed Kim Il Sung as the leader of North Korea — but he was not the Soviet Union’s first choice, as former Washington Post journalist Blaine Harden recounts in his excellent book, “The Great Leader and the Fighter Pilot.”

The Soviets’ first choice was a political leader known as “Korea’s Gandhi” but he was not a Communist and did not want the job. So they turned to Kim, who had a reputation in Korea as a heroic fighter in Manchuria against the Japanese.

But when the Soviets presented Kim as North Korea’s new leader to a huge crowd in Pyongyang, he did not impress, Harden writes in his book. Kim looked even younger than his 33 years, nervously read a speech written for him by his overlords, and had, in the words of one witness, a haircut “like a Chinese waiter.”

But Kim prevailed, largely thanks to a propaganda campaign waged by his Soviet patrons. This became the basis for the personality cult that pervades all aspects of North Korea to this day.

Kim Il Sung’s tenure

It’s hard to imagine it now, but in the first three decades of Kim Il Sung’s rule, North Korea was doing relatively well. The northern half of the country, long considered the “breadbasket” while the south was the industrial part, had enough food and had the support of its benefactors in the Soviet Union and China.

It wasn’t until the mid-1970s that South Korea’s economy overtook the North’s. Kim Il Sung traveled and struck up friendships with like-minded countries around the world — and there were many more of them back then. He was widely admired by North Koreans — and even today, defectors to the South often still have some affection for him.

All Kim, all the time

This, of course, was helped along by the all-encompassing personality cult that means Kim Il Sung’s portrait is hung in every building in North Korea — homes, factories, government buildings — as well as on street corners and railway stations and mountainsides. He’s the subject of many of the movies, music and books produced in North Korea.

The best university in North Korea is Kim Il Sung University; North Korea’s “self-reliance” doctrine is called “Kimilsungism”; those who excel at Kimilsungism might win the Kim Il Sung Prize. The central plaza in Pyongyang — and most other towns and cities — is Kim Il Sung Square. North Koreans wear a badge of Kim Il Sung (and sometimes Kim Jong Il too) over their heart. And of course, there are flower displays of the special orchid called Kimilsungia.

One of North Korea’s most common slogans is: “Kim Il Sung will live with us forever!” His embalmed body lies in the Kumsusan Palace of the Sun, a huge marble mausoleum in Pyongyang, where visitors must wear covers over their shoes. His son, Kim Jong Il, is now there too.

In the North Korean calendar, this year is not 2017 but “Juche 106” — because the first year of Kim Il Sung’s life is officially “Juche 1.” (Juche is the North Korean word for “self-reliance,” a concept it uses to suggest it doesn’t depend on anyone else, even while depending on China and, once, the Soviet Union.)

What purpose does this personality cult serve?

The Soviet Union collapsed, China instituted economic reforms, Cuba and Burma are opening up, but North Korea has remained steadfastly closed.

To keep the populace scared and unified — and most of all, closed off from the outside world — the North Korean regime has propagated this personality cult with the message that the “fatherly leader” Kim Il Sung and his two successors, Kim Jong Il and now Kim Jong Un, are taking good care of them.

Other authoritarian countries have had personality cults — look at Saddam’s Iraq, Gaddafi’s Libya and Turkmenistan under Turkmenbashi. But none has been as all-encompassing as North Korea’s. Basically, Kim Il Sung is god.

No dissent is tolerated. It is impossible to speak ill of the leaders in North Korea — it’s almost impossible to even think ill of them — without getting in serious trouble. Secret police and informants are everywhere to report anyone who even remotely criticizes the regime.

Through this repressive system, the Kims have been able to keep a grip on this state, against the odds, for 70 years.

North Korean leader Kim Jong Un cut the red ribbon at a ceremony celebrating the completion of a residential complex in Ryomyong street in Pyongyang, North Korea, two days before the anniversary of the birthday of North Korea's founder. (Reuters)

Hence the big deal about the Eternal President’s birthday?

Exactly. Having a huge celebration on this day reinforces this personality cult. The 100th anniversary of Kim Il Sung’s birth in 2012 was a huge deal — North Korea held a huge military parade, complete with missiles on trucks and jets flying overhead — and launched what they said was a long-range rocket to put a satellite into orbit. (It failed soon after it was fired.)

But by putting all these resources and all this time into celebrating North Korea’s founder, it perpetuates the deification of the Kims and their grip on this state.

There are signs that North Korea is preparing for a huge parade again this year — people have been practicing dancing in the square.

As part of the lead-up, Kim Jong Un cut the ribbon at the opening of one of his pet projects, Ryomyong Street, this week.

This central Pyongyang district — complete with a 70-story high rise, apartment buildings, restaurants and shops — is a marquee project in Kim’s efforts to make Pyongyang into a modern city and make the elite think their lives are getting better.

Pak Pong Ju, the North Korean premier, said the project “incorporates the latest architectural science and technology, including solar and geothermal technology, and the greening of roofs and walls,” according to reports from Pyongyang.

But what else does North Korea have in store? We’ll all just have to wait and see.