One million died and another million emigrated in the six years from 1845 to 1851. The population of Ireland was then about eight million, compared to only about 15 million or so on the British mainland. Descendants of the survivors who did not emigrate. Nationalists at a rally in Derry, 1996. But the reaction to that natural disaster is matter of fierce dispute.
Nationalist rhetoric claims it was genocide plain and simple.
The British wanted to crush Irish nationalism, then about 50 years old, in the bud and used any means available. Ireland was still exporting food well into the famine and the landlords' refusal to accept starvation as good reason not to pay the rent created a vicious circle. For hundreds of thousands, the eviction that followed was tantamount to a death sentence. There were two factors which led to the almost dependency of the Irish peasantry on the potato. First was the system of large estates belonging mostly to English or at least Anglo-Irish landlords, which squeezed peasants' own holdings into small holdings.