At the end of 1917, Nguyen Tat Thanh returned to France from England, when the Russian 1917 October Revolution had succeeded. The Revolution opened a new page in the history of Russia and the world in general, marking a new trend of social transformation.
Although several patriots and revolutionaries in the Eastern countries, such as Sun Yat-sen (China) and Phan Boi Chau (Vietnam), had good impressions on the October Revolution, they did not decide to follow the revolution’s example because they had not yet fully evaluated the impact of the revolution on the struggle for national independence in Eastern countries.
Meanwhile, young Vietnamese patriot Nguyen Tat Thanh quickly realised that this was a great historical event with a wonderful attraction that awakened the masses because it marked the first time that the working class established their own government.
From "sensory perception", with political acumen in addition to practical experience and research from documents, Nguyen Tat Thanh gained a deeper understanding of the Russian Revolution.
Like the shining sun, the October Revolution illuminated the five continents, and awakened millions and millions of oppressed and exploited people. In human history, there had never been a revolution with such great and profound significance.
President Ho Chi Minh
He also recognised the need to unite the struggle for national liberation of the peoples in Indochina with the struggle of the oppressed people in other colonial countries.
Talking about the meaning of the October Revolution to the colonial countries and peoples, President Ho Chi Minh later wrote: “Like the shining sun, the October Revolution illuminated the five continents, and awakened millions and millions of oppressed and exploited people. In human history, there had never been a revolution with such great and profound significance.” 
The Third International, established by V.I. Lenin in March 1919, created a turning point in the international communist and workers' movement as well as in the national liberation movement in the early 20th century.
V. I. Lenin’s draft thesis on national and colonial questions was published in L’Humanité Newspaper on June 16 and 17, 1920. The thesis was then presented by V.I. Lenin at the Second Congress of the Communist International, held from July 19 to August 7, 1920.
This was the first time Nguyen Ai Quoc had read a document that directly and strongly touched on what he was searching for. The thesis of V.I. Lenin created within him a strong emotional reaction. V.I. Lenin's arguments on national and colonial issues in the new context of the struggle against imperialism on a worldwide scale, which were presented in the thesis, caused Nguyen Ai Quoc to completely trust in Lenin and the Third International.
These arguments provided answers to the concerns and questions of Nguyen Ai Quoc on supporting the Second International or the Third International. He had a clear answer: Standing on V.I. Lenin's Third International. From V.I. Lenin’s ideology, Nguyen Ai Quoc found the support and source of strength to attain the goal of the national liberation.
During the second half of 1920, Nguyen Ai Quoc participated in debates with the help of comrades in the French Socialist Party such as Marcel Cachin, Paul Vaillant Couturier, Mongmusso, and others, which helped him to gain fundamental awareness of Marxism-Leninism and thus consolidate his political acumen.
Nguyen Ai Quoc speaks at the Congress of the French Socialist Party held in Tours (December, 1920).
On December 30, 1920, at the Tours Congress, Nguyen Ai Quoc voted in favour of the establishment the French Communist Party and became one of its founders . This was the decision to establish him as the first Vietnamese soldier following the revolutionary path of V.I Lenin.
In the dense darkness of colonialism, from an enthusiast patriot, Nguyen Ai Quoc became a pioneer revolutionary soldier and a communist.
Nguyen Ai Quoc pursued a completely different path from the previous revolutionaries. At that time, not only was Nguyen Ai Quoc a patriot who wanted to save the country, he found the right path for the national liberation revolution in following Leninism. It was his second important decision after the decision on heading the West to seek a way to save the country.
By studying and absorbing October Revolution and V.I Lenin's Thesis, then Marxism-Leninism, Nguyen Ai Quoc affirmed that it was the truest and most genuine theory.
Although there were many other theories appeared in the world in the 1920s and 1930s, Nguyen Ai Quoc soon identified that the Vietnamese people’s revolution for national liberation would follow the path of the Marxism-Leninism and the Russian October Revolution.
He wrote: “In today's world, only the Russian Revolution has succeeded, and it has truly succeeded. That is, the people enjoy true happiness of freedom. The Russian Revolution teaches us that a revolution succeeds only when the people (workers and peasants) played the key role, with strong party […] following Marxism–Leninism.” 
1. Complete Works of Ho Chi Minh (2011), National Political Publishing House, Volume 15, page 387.
2. Ho Chi Minh Biographical Chronicle (2006), National Political Publishing House, Volume 1, page 112.
3. Complete Works of Ho Chi Minh (2011), National Political Publishing House, Volume 2, page 304.