Short answers, pulled from the story.
Ho Chi Minh declared independence on the 2nd of September 1945 in Ba Dinh Square. He proclaimed the creation of the Democratic Republic of Vietnam to replace French rule and the Nguyễn dynasty.
The Geneva Conference ended the First Indochina War and affirmed Vietnamese independence by dividing the country along the 17th parallel. More than one million North Vietnamese migrated to South Vietnam following this partition under Operation Passage to Freedom.
A Politburo document dated the 4th of May 1953 set planned executions at a ratio of one per 1,000 people. Scholar Balasz Szalontai documented that 1,337 landlords were executed by December 1955 out of 62,182 identified targets.
China, the DPRK, and the Soviet Union provided aid and troops in support of North Vietnamese activities throughout the conflict. Other nations including Australia, the Republic of Korea, Thailand, and New Zealand contributed troops and military aid to South Vietnam.
Japan signed an agreement to establish diplomatic relations on the 21st of September 1973 in Paris. The document was written in French language and restored ties between the two nations before opening an embassy in Hanoi on the 11th of October 1975.