National Democratic Front was founded as an umbrella of various opposition movements in North Yemen

Yemen Arab Republic

The Yemen Arab Republic , also known as North Yemen or Yemen , was a country from 1962 to 1990 in the western part of what is now Yemen...

 on February 2, 1976 in San'a. The five founding organisations of NDF were the Revolutionary Democratic Party of Yemen

Revolutionary Democratic Party of Yemen

Revolutionary Democratic Party of Yemen was a political party in North Yemen, founded by a conference of the members of the Arab Nationalist Movement in North Yemen in June 1968. The conference resolved to break its organizational ties with the central structures of the ANM and form the...

, Organisation of Revolutionary Resistors of Yemen, the Labour Party, the Popular Vanguard and the People's Democratic Union.

On March 5, 1979, the five founding parties of the NDF merged to form the Yemeni Popular Unity Party. The NDF did however continue to exist as a separate structure. It was joined by Baath Party

Baath Party

The Arab Socialist Ba'ath Party was a political party mixing Arab nationalist and Arab socialist interests, opposed to Western imperialism, and calling for the renaissance or resurrection and unification of the Arab world into a single state. Ba'ath is also spelled Ba'th or Baath and means...

, led by Qassem Salaam, and the Septembrist Grouping. In 1978 the Baath Party left the front and in 1979 the June 13 Front of Popular Forces joined it.