The traditional Korean folk song Arirang filled the air and two divided nations marched as one in an emotional Winter Olympic Games Opening Ceremony in Pyeongchang. The flame was carried towards the cauldron by ice hockey players Park Jong-ah of South Korea and Jong Su-hyon from the North.

"We thought it would be a dramatic moment to go up together. My heart was overwhelmed," said ceremonies director Song Seung-whan.

Only two months earlier, North Korea’s leader Kim Jong-un talked of "glorifying a meaningful year" in a new thaw in Korean Peninsula relations.

"As for the Winter Olympic Games to be held soon in South Korea, we earnestly wish success," he said when announcing that North Korea would take part in a New Year's Day message.

"Since we are compatriots of the same blood as South Koreans, it is natural for us to share their pleasure over the auspicious event and help them."

The unification flag, mothballed since 2007, became familiar once again as the two nations marched together.

At the Opening Ceremony, South Korean leader Moon Jae-in welcomed Kim Jong-un's sister Kim Yo-jong to the Presidential box.

Before the year was out, there were face-to-face meetings between the two Korean leaders and even United States President Donald Trump, all arguably triggered by the overtures made in Olympic sport, and Moon made a speech at the Arirang Games in Pyeongchang celebrating 70 years of North Korea.

Not everyone supported the new moves and there were some demonstrators outside the stadium in Pyeongchang.

Many others remain guarded about what happens next. It had, after all, taken almost seventy years to reach this point and during that time apparent progress was often followed by confrontation.

Technically the two Koreas remain at war after a bitter conflict. An armistice was signed in 1953.

Within three years, the North sought entry to the Olympic family at the 1956 International Olympic Committee (IOC) Session in Melbourne.

Even then a unified team was a holy grail for the IOC. Chancellor Otto Mayer highlighted the "joint" team of East and West Germany, "suggesting similar arrangements be made in Korea".

Romania’s Alexandru Siperco quickly insisted "it would be impossible to make such an arrangement".

Even so, North Korea were provisionally recognised by the IOC in 1957 "only if they cooperate in forming one single team".

At the IOC’s 1959 session in Munich, Bulgaria’s general Vladimir Stoitchev described the North’s unsuccessful attempts to open dialogue.

Russian member Konstantin Adrianov accused the South of "dodging such an interview". He advised that a group from the North were waiting in Moscow and could come to Munich "at once". No agreement was reached, but North Koreans did compete at the 1964 Innsbruck Winter Olympics, where Han Pil-Hwa won silver in the 3,000 metres women’s speed skating event.

They were expected at the Tokyo Olympics but some were banned after they attended the 1963 Games of New Emerging Forces (GANEFO) in Jakarta because it was not sanctioned by international governing bodies including the International Amateur Athletics Federation (IAAF). Among those excluded were world-class women’s 800m runner Dan Sim Kim. The entire North Korean team withdrew.

In the meantime, North Korea's footballers qualified for the 1966 World Cup. They sensationally beat Italy 1-0 to reach the quarter-finals and led 3-0 before they were finally defeated by Portugal.

They might even have returned to the Olympics in 1968 but their participation at GANEFO II upset the IAAF. A naming dispute gave them the pretext to withdraw.

In 1972, détente was in the air. A joint communiqué containing three principles of peaceful re-unification was signed in early summer.

North Korea were in Munich for the Olympics. Small bore rifle shooter Li Ho Jun won gold but upset many when he said: "I thought I was shooting at my enemies." It may have lost something in translation.

Both Koreas took regular part in the Asian Games. In 1978, they came face to face in the men’s football final in Bangkok.

A crowd of 60,000 watched but, as The Times of India reported, "both goals lived a charmed life". It was 0-0 after extra time so the gold medal was shared.

North Korea did go to Moscow in 1980 but the South boycotted, before Seoul was voted as the 1988 Summer Olympic Games host city in 1981.

Pyongyang newspapers insisted "South Korea is not capable of undertaking such a large scale event" and talked of "a ridiculous hulabaloo about the Olympics".

Then, in 1983, a bomb attack killed leading South Korean politicians and officials at a mausoleum in Rangoon and the trail led back to North Korea.

Yet there were tentative suggestions of a united Korean team at the 1984 Los Angeles Olympics, which came to nothing, when the North boycotted once more.

When Seoul formally received the ceremonial Olympic Flag as the Games ended, the sniping transformed into a demand for Pyongyang to co-host in 1988.

It was always unlikely but IOC President Juan Antonio Samaranch tried to broker a deal. Four high-level meetings in the course of the next two years came to nothing.

Relations worsened after a South Korean airliner exploded killing 115 and a captured agent revealed it was on the direct orders of Pyongyang.

Only a handful of nations stayed away from Seoul 1988. North Korea was one of them.

Relations thawed again at the 1990 Asian Games, when Jan Sung shik, Chef de Mission of the South Korean team, met his North Korean counterpart Kim Hyung Jin and "unification" football matches were arranged. 

The North won 2-1 in Pyongyang. A fortnight later, 80,000 turned in Seoul for the return.

"This is not purely a sports festival, it should lead to a unification festival," said Kim Yu Sun, chairman of the North Korea Sports Guidance Committee.

United teams played in the FIFA World Youth Championships and World Table Tennis Championships but, in 1994, Korea’s founding leader Kim Il-sung died.

By this time, the design of a unification flag had been agreed but it was not seen at the Olympics until the year 2000. IOC President Juan Antonio Samaranch persuaded the Koreas to march together in Sydney.

"We are of the same blood," said Un Chang, IOC member in North Korea.

South Korean basketball player Chung Eun Sung carried the flag along side North Korean judoka Park Jeong-chul. Yet there was still politicking at the ceremony.

"I was told to put my hand on the flag pole higher than his," she recalled later.

At the 2002 FIFA World Cup, unification activists planned to display a huge flag at the South Korea versus Germany semi-final. The idea was eventually shelved because "it might prompt politically sensitive reactions", according to said supporters' leader Shin In-chul.

The flag was also flown at Asian Games and at the Universiades until 2007.

"There was a great willingness on the side of sport to have a joint march, both National Olympic Committees were in agreement," said then IOC President Jacques Rogge.

"Unfortunately the political powers both on the South and the North did not agree and I regret this very much because this is a setback for peace and harmony and reunification."

In 2012, relations were strained when the South Korean flag was mistakenly displayed on the scoreboard in Glasgow before North Korea’s women played their football preliminary against Colombia. Kick-off was delayed as they refused to play until the error was rectified.

By this time, Pyeongchang had been chosen as 2018 Winter Olympic hosts and IOC President Thomas Bach hinted that behind the scenes discussions were taking place. 

With only two months until the Opening Ceremony, they seized on North Korea’s overtures.

"As you know from the popular Korean folk song Arirang, it is a long journey across the cold mountains," Bach said as he greeted both sides in Lausanne three weeks later.

An agreement to an "Olympic Korean Peninsula Declaration" was then announced.

There were to be 22 athletes from the North - in figure skating, short track, cross-country skiing and alpine skiing. 

In ice hockey, 12 players would join the South Koreans to form a unified squad. They soon arrived to begin training with their new team-mates. 

Three of them were to be included in each match but final selection rested with Sarah Murray, the Canadian head coach .They wore distinct uniforms and even had their own acronym - COR.

At the village in Gangneung where the players were quartered, the North Korean block was by flanked South Korea and Japan, encapsulating the recent history of the peninsula.

The team scored only twice and lost every match despite the encouragement of 229 North Korean cheerleaders who wore matching red outfits and performed choreographed routines.

"I strongly feel we are one and hope we can bring ourselves together and build a united country," one of the cheerleaders told reporters.

"I believe its what everybody hopes for."

Not to be outdone, the South Koreans also choreographed special moves inside and outside the stadia.

"With your joint march you have shared your faith in a peaceful future. You have shown how sport brings people together in this fragile world," Bach said at the Closing Ceremony.

Within a month he was in North Korea for what were described by the IOC as "fruitful talks" with Kim Jong-un. These confirmed participation for Tokyo 2020.

A further chapter was written at the 2018 Asian Games in Jakarta and Palembang when a unified team won gold in women’s 500m dragon boating.

"It suddenly made me feel very patriotic," said team member Kim Hyeon Hee. "I was choked when I heard Arirang played on the podium."

Since then a joint communiqué from the two Korean leaders has expressed support for a joint bid for the 2032 Olympics.

If this were to happen, it would surely prove hard for the IOC to resist.