http://www.kavanaghfamily.com/articles/2003/20030618jfc.htm

In the 12 year period during and following the Confederation revolt, from 1641 to 1652, over 550,000 Irish were killed by the English and 300,000 were sold as slaves, as the Irish population of Ireland fell from 1,466,000 to 616,000. Banished soldiers were not allowed to take their wives and children with them, and naturally, the same for those sold as slaves. The result was a growing population of homeless women and children, who being a public nuisance, were likewise rounded up and sold. But the worse was yet to come.

In 1649, Cromwell landed in Ireland and attacked Drogheda, slaughtering some 30,000 Irish living in the city. Cromwell reported: "I do not think 30 of their whole number escaped with their lives. Those that did are in safe custody in the Barbados." A few months later, in 1650, 25,000 Irish were sold to planters in St. Kitt. During the 1650s decade of Cromwell's Reign of Terror, over 100,000 Irish children, generally from 10 to 14 years old, were taken from Catholic parents and sold as slaves in the West Indies, Virginia and New England. In fact, more Irish were sold as slaves to the American colonies and plantations from 1651 to 1660 than the total existing "free" population of the Americas!

But all did not go smoothly with Cromwell's extermination plan, as Irish slaves revolted in Barbados in 1649. They were hanged, drawn and quartered and their heads were put on pikes, prominently displayed around Bridgetown as a warning to others. Cromwell then fought two quick wars against the Dutch in 1651, and thereafter monopolized the slave trade. Four years later he seized Jamaica from Spain, which then became the center of the English slave trade in the Caribbean.