The Democratic Republic of Vietnam (VietnameseViệt Nam Dân Chủ Cộng Hòa), also known as North Vietnam, was founded by Ho Chi Minh and was recognized by China and the USSR in 1950. In 1954 after the defeat of France at the Battle of Dien Bien Phu, France formally recognized the DRV and the country was partitioned in two.
Following the partition of the country, there followed a mass exodus of North Vietnamese to the South, many of them Catholics who claimed that North Vietnamese policy towards them amounted to persecution. In its early years, the poor nation, cut off from the agricultural areas of the South, is described by many as having become repressive and totalitarian. Between 1955 and 1956, agragrian reforms were attempted — these have widely been condemned as brutal and ineffectual. In 1959, the Vietnamese Communist Party secretly decided to help the war effort in the South, despite enormous costs.
Ho Chi Minh and the proclamation of the Republic of Vietnam
That was the general situation in Vietnam when Ho Chi Minh and his comrades from the Communist Party of Indochina and subsequently of Vietnam, founded by him, proclaimed a sovereign and independent republic, disposed to help liberate its sister colonies of Laos and Cambodia as soon as humanly possible.
To the north, the DemocraticRepublic of Vietnam, with its capital in Hanoi, and to the south, the Republic of South Vietnam, with its capital in Saigon.
The reasons why countries call themselves DemocraticRepublics are also very different from case to case, but the common denominator seems to be that all these countries were created as a result of a revolution or war of independence against a domestic or foreign regime that was widely seen as tyrannical, oppressive and undemocratic.
This may be the reason why DemocraticRepublics tend to be either ex-colonies (Congo, Sri Lanka, Algeria, etc.) who achieved independence after breaking away from an imperialist power, or communist states that were created after the overthrow of a capitalist regime (since communists regard capitalism as inherently undemocratic).
In particular, the German DemocraticRepublic (East Germany) and the Democratic People's Republic of Korea (North Korea) gave themselves the title of "DemocraticRepublics" as a way of implying that their rivals - West Germany and South Korea - were not democratic.