Faiz Ahmad was a Marxist and believed in the idea of an egalitarian society. When he writes, ‘those dark and brutal curses of countless centuries’, he probably means the suffering caused by stark poverty which seems to be a brutal curse on the hapless poor. The phrase ‘countless centuries’ suggests that the poor have no escape from this state of want. At another level, the phrase can be taken as having political allusions. It highlights the betrayal of the founding of Pakistan.
It is to be read as addressed to the nation of Pakistan, which Faiz had embraced with much hope, and with whose political leaders he became disillusioned. The persecution of minorities, martial laws, public floggings and public executions changed the nature of the creation of Pakistan as a nation. The vulnerable were no longer safe in the land created to protect them.