In 1955, Tambo became Secretary General of the ANC after Sisulu was banned by the South African government under the Suppression of Communism Act.
Ngonyaka ka-1955, uTambo waba nguNobhala-Jikelele we-ANC ngemuva kokuthi uSisulu enqatshelwe nguhulumeni waseNingizimu Afrika ngaphansi koMthetho Wokuqinisa Ubukhomanisi.