After the Japanese Meiji Restoration in 1868, a modern industrial state and a modern military were built for Japan by Britain and the United States over the next decades. By the turn of the century the Russian Trans Siberian railroad was completed and Czar Nicholas II sought a permanently open port at Port Arthur in Manchuria because the Russian port at Vladivostok was closed by ice much of the year.
Since Manchuria and Korea had long been in the Japanese sphere of influence, the 1904 – 1905 Russo Japanese War broke out and Russia was defeated by Japan.
In 1910 Japan annexed Korea and Manchuria and along came WW I, followed by the Bolshevik Revolution in Russia.
By the mid 1920’s American British and Russian generated resistance to the Japanese in Manchuria grew.
In China proper, Russia backed a Communist Movement led by Mao and the US backed a Nationalist Movement led by Chang Ki-shek against Japan.
Later after the fall of Japan in WW II, these two movements fell to fighting one another.
These movements in China and Manchuria resulted in a similar situation in Korea with the communists mounting a guerrilla movement to fight Japan backed by Russia under Kim Il-sung, who had received military training in Russia and been sent to organize resistance in Korea as a major in the Soviet army. Not to be outdone America sent Syngman Rhee to lead a nationalist movement backed by the United States
With the defeat of Japan, Russia and the US agreed to divide Korea at the 38th parallel until the country could be unified. This move was to separate American and Russian troops while about 700,000 Japanese were being evacuated to Japan, and allow time for an indigenous government to be formed since Korea at that time had no history of independent governance.
Quickly the two sides began to consolidate their hold on the respective regions with the Russian controlled North putting down all American sponsored nationalists and the US military controlled South making similar efforts against the communists.
The two sides could not agree on a formula that would produce a unified Korea, and in 1947 U.S. President Harry S. Truman persuaded the United Nations (UN) to assume responsibility for the South, although the U.S. military remained in control of the South as a UN Trust.
In 1948 with American backing South Korea declared itself independent and in August 1948, Syngman Rhee became the first president of the newly declared Republic of Korea.
Backed by the US, Rhee then burned villages and summarily executed thousands of suspected political opponents and communists without trial. Hundreds more of Rhee’s political opponents were rounded up and sent to prisons across the country following dubious convictions of rebellion.
The fighting expanded into a limited border war between the South’s newly formed Republic of Korea Army (ROKA) and the North Korean border constabulary as well as the North’s Korean People’s Army (KPA). The North launched cross-border guerrilla incursions in order to draw ROKA units away from their campaign against opponents of the Rhee dictatorship in the South.
Finally on June 25, 1950 North Korea invaded the South in an attempt to unity the country. The war lasted until 1953 killing over one million people and accomplished exactly nothing with a new ceasefire line set at the 38th parallel.
With the Chinese Russian falling out in the 1950’s and 60’s North Korea came into the Chinese fold. Since then China has moderated its policies while North Korea has ended up a feudal state ruled by a handful of families for personal gain, maintaining the fiction of being a communist state.
South Korea has prospered as has Japan over the past decades while North Korea like all feudal systems has stagnated and fallen far behind in terms of the public good. To maintain their position it has been necessary to maintain a “us against the world” belief in the masses whipping up fear of external threats and following that up with militarist bombast.