In the thousands of years of East Asian history, a very large number of states have come and gone. Some have left a prominent mark on the world, while others have faded into obscurity. But even if we limit ourselves to the past few centuries, there are quite a few countries in East Asia's modern history that you may have never heard of, and the circumstances that lead to their creation are quite fascinating. Let's explore!

Correction:
4:58 Koxinga is pronounced "Kok-sèng-iâ" in his native Hokkien

Countries that appear in this video:
Tibet
Dzungar Khanate
Uryankhay Republic / Tannu Tuva
Jaxa
Zheltuga
Taiping Heavenly Kingdom
Heavenly Kingdom of Great Mingshun
Tungning
Ezo
Republic of Formosa
Japanese puppet states in China (incl. Manchukuo, Mengjiang, Wang Jingwei regime, and more)
Ryukyu
1st and 2nd East Turkestan Republics
Korean People's Association in Manchuria
People's Republic of Korea
All the Russian Civil War states (incl. Green Ukraine, Provisional Government of the Far East, Far Eastern Soviet Republic, Tungus Republic, Buryat-Mongolia, and more)
All the 1911 Revolution states (incl. Beiyang government, Empire of China, KMT government, and more)
All the Chinese communist states (incl. Chinese Soviet Republic and its very numerous constituents, Fujian People's Government, and more)
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Image credits:

You may use the any slide containing a CC-BY-SA work under a CC-BY-SA 4.0 license

Jaxa Coat of Arms: By Tadeusz Gajl – projejt graficzny & Bastianow (Bastian) – wersja wektorowa, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...

Formosa Flag: By Jeff Dahl - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...

Wang Jingwei Flag: By SVG file created by User:Mononomic on en.wikipedia.org. - 中華民國，南京國民政府, CC BY 3.0, https://commons.wikimedia.org/w/index...

Note the flag used here for Ryukyu only shows up in mainland Japanese sources, and Ryukyu may not have had a flag at all.

Far Eastern Republic Flag: By NuclearVacuum - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...

Bogd Khanate Flag: By Joins2003, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...

Fujian People's Government Flag: By Froztbyte - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...

Hand gesture with gap: By Twitter, CC BY 4.0, https://commons.wikimedia.org/w/index...

"NATIONAL ナショナル Clock 時計 Pagoda, 'Clock of Peace' Senso - Ji Temple Asakusa Tokyo Japan" by Arjan Richter is marked with CC BY 2.0

Tibet Locator: By Don-kun; original: User:TUBS - Own work, derivate of File:Bhutan in Asia.svg, CC BY 3.0, https://commons.wikimedia.org/w/index...

Uryankhay map: By Flalf, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...

Women world leaders: By Scottish Government - https://www.flickr.com/photos/scottis..., CC BY 2.0, https://commons.wikimedia.org/w/index...

Amur: By Kmusser, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...

PLC: By Tonhar, CC BY 3.0, https://commons.wikimedia.org/w/index...

Revenge: By User:Rama, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...

Amur photo: "Ozero Katar,Amur River Island" by sussexbirder is marked with CC BY 2.0

Hong Xiuquan By Jakob Montrasio from Saarbrücken, Germany - Nanjing, China.Uploaded by MtBell, CC BY 2.0, https://commons.wikimedia.org/w/index...

Taiping Map: By Kalem000 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index...

Taipei: By Jirka Matousek, CC BY 2.0, https://commons.wikimedia.org/w/index...

Tungning map: By Luuva, CC BY 3.0, https://commons.wikimedia.org/w/index...

Japan blank map: By Maximilian Dörrbecker (Chumwa), CC BY-SA 3.0, https://commons.wikimedia.org/w/index...

The Three Mountains: By Bhasker Garudadri|garudadri.org - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index...

Anarchists: By The original uploader was Jsymmetry at English Wikipedia. - Transferred from en.wikipedia to Commons., CC BY 3.0, https://commons.wikimedia.org/w/index...