KNS / KCNA VIA KNS / AFP
Seoul - The first sign that Kim Jong Un was making his inaugural overseas trip as leader of North Korea was the appearance of an armoured train in China.
His predecessors, father Kim Jong Il and grandfather Kim Il Sung, also preferred rail for their domestic and overseas travels.
International childhood, domestic rule
Kim Jong Un studied in Switzerland in the 1990s, including at the International School of Berne, along with his brother and sister, and is believed to have visited Germany and France during the period.
Unconfirmed South Korean news reports said Jong Un and his brother Jong Chol visited Tokyo Disneyland as children using fake passports to enter Japan in 1991.
Infamously his eldest brother Jong Nam - assassinated at Kuala Lumpur's international airport last year in a killing widely blamed on Pyongyang - tried to do the same in 2001, using a Dominican Republic passport, but was stopped at Japanese immigration.
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Kim Jong Un is known to travel by air domestically, and is said to have accompanied his father on a 2011 train trip to China, but is believed to have not previously left the North since ascending to power.
In 2015 the Kremlin announced Kim would be attending ceremonies to mark the 70th anniversary of the Soviet Union's victory over Nazi Germany in World War II, but in the end the visit was cancelled with no reason given.
Chinese President Xi Jinping (2nd right), his wife Peng Liyuan (right), North Korean leader Kim Jong Un (2nd left) and his wife Ri Sol Ju (left) posing during their meeting in Beijing on 27 March, 2018. (Photo: CCTV / AFP)
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Fear of flying
Kim's father Kim Jon Il was renowned for his fear of flying, limiting his foreign trips to overland journeys to China and Russia by armoured train - the same mode of transport used to reach Beijing this week.
His 2011 trip to China was a marathon 6 000 kilometre journey taking in Beijing, Nanjing and Shanghai among other destinations.
One of his previous visits came in 2000, shortly before the first inter-Korean summit with South Korean president Kim Dae-jung.
This file picture taken on 7 May, 2010 and released by North Korea's official Korean Central News Agency (KCNA) on 11 May, 2010 shows North Korean leader Kim Jong-Il (C) waving from a train while leaving the Chinese capital of Beijing ending his five-day visit to China. (Photo: KNS / KCNA via KNS / AFP)
Kim Jong Il also took trains to Russia in 2001, when he went to Moscow, and 2011, when he met then-president Dmitry Medvedev in the Siberian city of Ulan-Ude.
At the time residents near the Bureya rail station were told to stay in their houses and not look out of their windows as his armoured train arrived.
Police officers keeping watch next to a train at the Beijing Railway Station on Tuesday. (Photo: Jason Lee / Reuters)
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Of the three Kims, the North's founding father Kim Il Sung was the most frequent overseas traveller.
He secretly visited Moscow in 1949 to meet Stalin and seek support for his plan to reunify the divided Korean peninsula by force.
The following year, Kim Il Sung's forces invaded the South, triggering the Korean War that pitted Pyongyang's Chinese and Russian-backed troops against a US-led United Nations alliance.
In 1961, Kim Il Sung returned to Moscow to meet then-General Secretary Nikita Khrushchev and the two countries signed a mutual defence pact.
A man watches a television news report about a suspected visit to China by North Korean leader Kim Jong Un, at a railway station in Seoul on 27 March, 2018. (Photo: Jung Yeon-je / AFP)
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He was a prominent figure in the Non-Aligned Movement and attended a conference of Asian and African countries in 1965 in Bandung, Indonesia, bringing along his son.
In 1990, he travelled secretly to China, reportedly to discuss warming relations between South Korea and the Soviet Union with Chinese leaders including Jiang Zemin.
Kim Il Sung's longest train trip took place in 1984, on a tour of the Soviet Union and other East European countries - Poland, East Germany, Czechoslovakia, Hungary, Yugoslavia, Bulgaria and Romania.
This file picture taken on 21 August, 2011 and released on 29 August, 2011 by North Korea's official Korean Central News Agency (KCNA) shows North Korean leader Kim Jong Il (R) being welcomed by Russian women in traditional dress at the Bureya station in Russia's Amur region. (Photo: KNS / KCNA via KNS / AFP)
The carriages Kim Il Sung and Kim Jong Il used for their travels are both on display in the Kumsusan mausoleum in Pyongyang where their bodies lie in state - with a Macintosh computer on Kim Jong Il's desk.