Primorsky Krai in the context of "Japanese intervention in Siberia"

Manchuria is a historical region in northeast Asia encompassing the entirety of present-day northeast China and parts of the modern-day Russian Far East south of the Uda River and the Tukuringra-Dzhagdy Ranges. The exact geographical extent varies depending on the definition: in the narrow sense, the area constituted by three Chinese provinces of Heilongjiang, Jilin, and Liaoning as well as the eastern Inner Mongolian prefectures of Hulunbuir, Hinggan, Tongliao, and Chifeng; in a broader sense, historical Manchuria includes those regions plus the Amur river basin, parts of which were ceded to the Russian Empire by the Manchu-led Qing dynasty during the Amur Annexation of 1858–1860. The parts of Manchuria ceded to Russia are collectively known as Outer Manchuria or Russian Manchuria, which include present-day Amur Oblast, Primorsky Krai, the Jewish Autonomous Oblast, the southern part of Khabarovsk Krai, and the eastern edge of Zabaykalsky Krai.

The name Manchuria is an exonym (derived from the endonym "Manchu") of Japanese origin. The history of "Manchuria" (Manzhou) as a toponym in China is disputed, with some scholars believing it was never used while others believe it was by the late 19th century. The area was historically referred to by various names in the Qing dynasty such as Guandong (East of the Pass) or the Three Provinces referring to Fengtian (Liaoning), Heilongjiang, and Jilin. Manchuria as a geographical term was first used in the 18th or 19th centuries by the Japanese before spreading to Europe. The term was promoted by the Empire of Japan in support for the existence of its puppet state, Manchukuo. Although the toponym is still used, some scholars treat the term with caution or avoid it altogether due to its association with Japanese colonialism. The term is deprecated in China due to its association with Japanese imperialism and ethnic connotations. As a result, areas once considered part of Manchuria are simply referred to as the Northeast. The Three Provinces and the Northeast were also in concurrent use among the Japanese along with Manchuria until the Mukden incident of 1931.

Khabarovsk Krai (Russian: Хабаровский край, romanized: Khabarovskiy kray, IPA: [xɐˈbarəfskʲɪj kraj]) is a federal subject (a krai) of Russia. It is located in the Russian Far East and is administratively part of the Far Eastern Federal District. The administrative centre of the krai is the city of Khabarovsk, which is home to roughly half of the krai's population and the largest city in the Russian Far East (just ahead of Vladivostok). Khabarovsk Krai is the third-largest federal subject by area, and had a population of 1,343,869 as of 2010.

Being dominated by the Siberian High winter cold, the continental climates of the krai see extreme freezing for an area adjacent to the sea near the mid-latitudes, but also warm summers in the interior. The southern region lies mostly in the basin of the lower Amur River, with the mouth of the river located at Nikolaevsk-on-Amur draining into the Strait of Tartary, which separates Khabarovsk Krai from the island of Sakhalin. The north occupies a vast mountainous area along the coastline of the Sea of Okhotsk, a marginal sea of the Pacific Ocean. Khabarovsk Krai is bordered by Magadan Oblast to the north; Amur Oblast, Jewish Autonomous Oblast, and the Sakha Republic to the west; Primorsky Krai to the south; and Sakhalin Oblast to the east.

Vladivostok (/ˌvlædɪˈvɒstɒk/ VLAD-iv-OST-ok; Russian: Владивосток, lit. '"Ruler of the East"', IPA: [vlədʲɪvɐˈstok] ) is the largest city and the administrative center of Primorsky Krai and the capital of the Far Eastern Federal District of Russia. It is located around the Golden Horn Bay on the Sea of Japan, covering an area of 331.16 square kilometers (127.86 square miles), with a population of 603,519 residents as of 2021. Vladivostok is the second-largest city in the Far Eastern Federal District, as well as the Russian Far East, after Khabarovsk. It is located approximately 45 kilometers (28 mi) from the China–Russia border and 134 kilometers (83 mi) from the North Korea–Russia border.

Vladivostok was historically part of Outer Manchuria. Shortly after the signing of the Treaty of Aigun between Qing China and the Russian Empire and affirmed by the Convention of Peking – from which it is also known as the Amur Annexation – the city was founded as a Russian military outpost on July 2, 1860. In 1872, the main Russian naval base on the Pacific Ocean was transferred to the city, stimulating its growth. In 1914 the city experienced rapid growth economically and ethnically diverse with population exceeding over 100,000 inhabitants with slightly less than half of the population being Russians. During this time, large Asian communities developed in the city. The public life of the city flourished; many public associations were created, from charities to hobby groups. After the outbreak of the Russian Revolution in 1917, Vladivostok was occupied in 1918 by White Russian and Allied forces, the last of whom, from the Japanese Empire, were not withdrawn until 1922 as part of its wider intervention in Siberia; by that time the antirevolutionary White Army forces had collapsed. That same year, the Red Army occupied the city, absorbing the Far Eastern Republic into the Russian Soviet Federative Socialist Republic. Following the dissolution of the Soviet Union in 1991, the city became a part of the Russian Federation.

Heilongjiang is a province in northeast China. It is the northernmost and easternmost province of the country and contains China's northernmost point (in Mohe City along the Amur) and easternmost point (at the confluence of the Amur and Ussuri rivers).

The province is bordered by Jilin to the south and Inner Mongolia to the west. It also shares a border with Russia (Amur Oblast, Jewish Autonomous Oblast, Khabarovsk Krai, Primorsky Krai and Zabaykalsky Krai) to the north and east. The capital and the largest city of the province is Harbin. Among Chinese provincial-level administrative divisions, Heilongjiang is the sixth-largest by total area, the 20th-most populous, and the second-poorest by GDP per capita after only Gansu province.

Jilin is one of the three provinces of Northeast China. Its capital and largest city is Changchun. Jilin borders North Korea (Rasŏn, North Hamgyong, Ryanggang and Chagang) and Russia (Primorsky Krai) to the east, Heilongjiang to the north, Liaoning to the south, and Inner Mongolia to the west.

Along with the rest of Northeast China, Jilin underwent an early period of industrialization. However, Jilin's economy, characterized by heavy industry, has been facing economic difficulties with privatization. This prompted the central government to undertake a campaign called "Revitalize the Northeast". The region contains large deposits of oil shale.

The Ussuri (/uːˈsʊəri/ oo-SOOR-ee; Russian: Уссури [ʊsˈsurʲɪ]) or Wusuli (Chinese: 乌苏里; pinyin: wūsūlǐ [ǔsǔlî]) is a river that runs through Khabarovsk and Primorsky Krais, Russia and the southeast region of Northeast China in the province of Heilongjiang. It rises in the Sikhote-Alin mountain range, flowing north and forming part of the Sino-Russian border (which is based on the Sino-Russian Convention of Peking of 1860), until it joins the Amur as a tributary near Khabarovsk. It is approximately 897 km (557 mi) long. The Ussuri drains the Ussuri basin, which covers 193,000 km (75,000 sq mi). Its waters come from rain (60%), snow (30–35%), and subterranean springs. The average discharge is 1,620 m/s (57,000 cu ft/s), and the average elevation is 1,682 metres (5,518 ft).

Between 1858 and 1860, the Russian Empire annexed territories adjoining the Amur River belonging to the Chinese Qing dynasty through the imposition of unequal treaties. The 1858 Treaty of Aigun, signed by the general Nikolay Muravyov representing the Russian Empire and the official Yishan representing Qing China, ceded Priamurye—a territory stretching from the Amur River north to the Stanovoy Mountains, but the Qing government initially refused to recognize the treaty's validity. Two years later, the Second Opium War concluded with the Convention of Peking, which affirmed the previous treaty as well as an additional cession including the entire Pacific coast to the Korean border, as well as the island of Sakhalin to Russia. These two territories roughly correspond to modern-day Amur Oblast and Primorsky Krai, respectively. Collectively, they are often referred to as Outer Manchuria, part of the greater region of Manchuria.

The Taz (Russian: Та́зы, romanized: Tázy; Chinese: 塔兹; pinyin: Tǎzī) are a mixed Sinitic and Tungusic ethnic group who primarily live in Primorsky Krai, Russia. The Taz people emerged from intermarriages between Han Chinese men and Tungusic women of the Udege, Nanai, and Oroch ethnic groups in Outer Manchuria. Today, the Taz primarily speak Russian, but their traditional language is the Taz dialect, a variety of Northeast Mandarin with loanwords from Udege and Nanai. The modern ethnonym "Taz" is a Russified version of the Chinese term tazi (meaning "indigenous, native").