Alexander Hassenstein/Getty Images AsiaPac/Getty Images
The national flag of South Korea with the Olympic flag at the Pyeongchang 2018 Olympic Village. The Olympic flag was designed by Pierre de Coubertin, founder of the International Olympic Committee, in 1913, but it only officially debuted at the Summer Games of 1920 in Antwerp, Belgium. The rings represent the world's five inhabited continents, but their colors were chosen by Coubertin because all of the world's flags at the time could be made from them (including the white of the background.)
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South Koreans wave unification flags as North Korean athletes arrive in Busan, South Korea, for the 2002 Asian Games. The Korean Unification Flag was first used in 1991, and has been used by the two nations at the opening ceremonies of the 2000, 2004 and 2006 Olympic Games.
DAMIEN MEYER/AFP/AFP/Getty Images
The flag of Nepal, seen here at the opening ceremony of the 2014 Winter Games in Sochi, is the only non-quadrilateral national flag in the world. It is composed of two combined triangles, and it's the only national flag that is flown at Olympic parades of nations in a format other than a rectangle.
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Only two national flags are perfect squares: Switzerland, shown here, and Vatican City.

"But you rarely see that shape (of the Swiss flag). You've got the official shape and then what people actually make it, and you quite often see a Swiss flag made to be rectangular," said Bartram.
The flag of Norway, by complete coincidence, contains the flags of Indonesia, Poland, Finland, France, the Netherlands and Thailand, which has earned it the nickname "mother of all flags."
MUSTAFA OZER/AFP/AFP/Getty Images
The flag of Mozambique includes an AK-47 rifle as a reference to the country's difficult transition to independence.

"Mozambique was a Portuguese possession, and the Portuguese did an appalling job of decolonization. It was utterly unforgivable. As a result, Mozambique had a very bloody start as an independent country, and the rifles they used were AK-47s because they were cheap and available. When they achieved independence and set up their government, they put it on their flag as a symbol of their struggle," said Bartram.

Other national flags include images of weapons too. "Guatemala has crossed rifles, Haiti has cannons. You do get some weird things on flags, but as long as they make sense to the people the flag belongs to, that's what counts."
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Is the US flag on military uniforms reversed when it is placed on the right shoulders of soldiers? "It isn't. You're just seeing the other side of it. If you imagine someone carrying a flag on a pole, and marching forward, that's the way the flag flies. The front edge of the flag goes at the front. If you did it the other way, it would look like the troops were marching backwards. On the American flag this looks obvious, but the British do it too and it's just more subtle due to the design of the flag," said Bartram.
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A 525-foot flagpole towers over the North Korean village of Kijong, near the Demilitarized Zone (DMZ) dividing the two Koreas. The village itself is designed to convey an idyllic image of North Korea, and some of the buildings are thought to be just facades. In the 1980s, South Korea erected a 323-foot flagpole, to which the North responded with one of their own, the tallest in the world at the time.
GUILLERMO LEGARIA/AFP/AFP/Getty Images
The white flag was recognized as a symbol of truce in the Hague Convention on land warfare of 1907, and anyone carrying a white flag must not be fired upon. But why white?

"Probably because that's the one sort of thing that you'd actually have available. If you made purple the color of surrender, that would be tricky, but a white cloth is always around -- a handkerchief, a vest. It doesn't even need to be white, it just needs to be undyed cloth, and that's usually easy to find," said Bartram.
The Filipino flag is the only one that is flown differently in times of peace and war, with the blue at the top when the nation is not in a state of war. This led to an international faux pas in 2010, when the flag was flown upside down during an event in New York.
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In 2016, New Zealand held a referendum to change its national flag, which includes the British Union Flag and was deemed to be too similar to Australia's. Pitted against the winning design from a preliminary referendum (center in the photo), the old flag won the popular vote with 56.6%.
Ted Soqui/Corbis News/Corbis via Getty Images
The Union Flag, or Union Jack, is the national flag of the United Kingdom and is present in many other national flags, including Australia, New Zealand, Tuvalu, Fiji and Bermuda. It's also part of the state flag of Hawaii (below in the photo), as the islands were once associated with the British Empire. It is the only US state flag to incorporate a foreign flag.
The flag of Ethiopia was the first to feature the pan-African colors red, green and gold, which were then picked up by Ghana.

"That was deliberate, as Ethiopia was the only sub-Saharan African country that wasn't colonized. When Ghana became independent, the first sub-Sarahan country to do so, it chose to use Ethiopia's colors as a basis for their flag because of its continuing Independence," said Batram. The colors were subsequently adopted by several other African countries.
Thomas Trutschel/Photothek/Photothek via Getty Images
Flags are among the world's oldest designs, and many countries have a claim for the world's oldest flag, including Denmark, which maintains its flag originated in 1219.

"But the claim is based on a legend, and other countries also have legends that say where their flags came from, like Scotland and Austria. The problem is that they're legends, and there's not really any documentary evidence," said Bartram.

Denmark, though, does hold the Guinness World Record for the oldest continuously used national flag (since 1625).
LEON NEAL/AFP/AFP/Getty Images
The stars in the European Union flag do not represent the member states. The number is fixed at 12, and never updated. "Technically it doesn't even represent the European Union, since it was originally the flag of the Council of Europe. It wasn't invented by the EU, and the stars are there because 12 is a nice number, with no political connotations," said Bartram.
The only two virtually identical flags are Chad and Romania (the blue strip of Chad's flag is darker than that of Romania's) but others are quite similar.
Bartram designed an unofficial flag of his own for Antarctica: "It was more of an accident than a plan. I was working on an electronic atlas of the world and each country had a national flag, except Antarctica. Antarctica is disputed, as several countries have claims to bits of it, so I needed to come up with something politically neutral. I followed the UN's (flag) model: a light blue flag and a map on top of it, just like the Korean Unification Flag, but with colors reversed. It also helps that Antarctica is mainly white and it sits on a blue thing," he said.
CNN  — 

When the flags of the world got their spotlight moment at this year’s Winter Olympics in PyeongChang, they were unified by two principles: sportsmanship and uniformity.

“Flags come in lots of different shapes, not just square and rectangular, and the rectangular ones are different shapes. They can be 2 by 3, like France, or 10 by 19, like the American one,” Graham Bartram, an expert at the Flag Institute, the world’s largest flag organization, said in a phone interview.

National flags come in more than a dozen different ratios, from the perfectly square Switzerland to the very stretched Qatar, the only flag whose width is more than twice its height. But at the Olympics, for the sake of practicality, they are all the same.

“It used to be that the ratio was made to follow the one of the host country, but now it’s been standardized to the Olympic flag, so at ceremonies they are all 2 by 3,” said Bartram.

National flags come in different shapes.

The only exception in Nepal, whose flag is not even quadrilateral. It is composed of two combined triangles, and allowed to fly proudly untouched (although not in PyeongChang, where Nepal did not compete.)

Korea’s unification flag

But perhaps the most significant unification came from North and South Korea, which marched together under one flag. It has happened before – even at the Olympics, in 2000, 2004 and 2006 – but it struck a chord in the current political climate.

The Korea Unification Flag has a simple design: a blue silhouette of the Korean peninsula on a white background. But in some versions of it, if you look closely, you can just about make out a dot on the right, meant to represent a small group of disputed islets known as the Liancourt Rocks. They are controlled by South Korea – which calls them “Dokdo” – but also claimed by Japan – which refers to them as “Takeshima.”

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The Korea unification flag showing a set of disputed islands.

Flags with the dot were seen at a practice hockey match just days before the Olympics, fueling diplomatic tensions between South Korea and Japan, which opened a permanent exhibition in Tokyo last month illustrating Takeshima and other territories that fuel separate disputes with China. In response to Japan’s complaints, South Korea’s unification ministry confirmed that a flag without the dot was used during the games, as approved by the International Olympic Committee.

It was the last flag to enter the parade, as the host country traditionally closes it. Greece, the nation who originated the Olympic Games, always opens the parade, while the rest of the order is alphabetical according to the language of the host nation. This led to an interesting opening quintet, based on the Korean alphabet: Greece, Ghana, Nigeria (making its Winter Olympics debut), South Africa, Netherlands.

A shade of blue

Just 91 flags paraded in PyeongChang, as opposed to the 207 seen at the 2016 Summer games in Rio. However, two of those flown in Rio were virtually identical: Chad and Romania.

Many flags are similar, but only two are identical.

“What happened was that once communist rule ended, Romania got rid of a badge it had in the middle, but then Chad complained, as that made it identical to their flag,” Bartram said. (In reality, the blue strip of Chad’s flag is darker than that of Romania’s.)

Rules and customs around flag design make duplicates unlikely, but several national flags are quite similar. That’s probably why a unique design stands out, as is the case of the UK’s Union Jack.

“It’s a very complicated design, it takes a lot of time to draw it. It’s rotationally symmetrical – not horizontally or vertically symmetrical – but it’s unique. There’s not quite anything like it,” Bartram said. “Even America has strong similarities with Liberia and Puerto Rico, but with the Union Jack one never wonders which flag it is. From a design point of view, it’s very powerful and recognizable.”

According to Bartram, however, the most remarkable flag design belongs to South Africa.

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The South African flag.

“Technically, it breaks all the rules. Flags are only meant to have three colors, but this one has six, and it works,” he said.

“Usually a flag is a reflection of the country, it comes after the country does, but this one was part of the creation of the country itself. It had a job to do. It was created to bring people together, and its symbolism indicates that. It actually helped create the country, and that’s very powerful.”