It was initially unclear how the chosen term was to be used—a letter written by Mawema in 1961 refers to "Zimbabweland" — but "Zimbabwe" was sufficiently established by 1962 to become the generally preferred term of the black nationalist movement. In a 2001 interview, black nationalist Edson Zvobgo recalled that Mawema mentioned the name during a political rally, "and it caught hold, and that was that". The black nationalist factions subsequently used the name during the Second ''Chimurenga'' campaigns against the Rhodesian government during the Rhodesian Bush War of 1964–1979. Major factions in this camp included the Zimbabwe African National Union (led by Robert Mugabe from 1975), and the Zimbabwe African People's Union (led by Joshua Nkomo from its founding in the early 1960s).