It was during the second half of the 17th century that occurred the "Cavalier" immigration that took place as a consequence of the overthrow of Charles I. Upon this subject there has been much misapprehension. Many persons have supposed that the followers of the unhappy monarch came to Virginia by the thousand to escape the Puritans, and that it was from them that the aristocracy of the colony in large part originated. Even so eminent a historian as John Fiske has been led into the erroneous belief that this immigration was chiefly responsible for the great increase in population that occurred at this time. "The great Cavalier exodus," he says, "began with the king's execution in 1649, and probably slackened after 1660. It must have been a chief cause of the remarkable increase of the white population of Virginia from 15,000 in 1649 to 38,000 in 1670."[27] This deduction is utterly unwarranted. The increase in population noted here was due chiefly to the stream of indentured servants that came to the colony at this period. At the time when the so-called Cavalier immigration was at its height between one thousand and fifteen hundred servants were sent to Virginia each year. In 1671 Governor Berkeley estimated the number that came over annually at fifteen hundred, and it is safe to say that during the Commonwealth period the influx had been as great as at this date. The constant wars in Great Britain had made it easier to obtain servants for exportation to America, for thousands of prisoners were disposed of in this way and under Cromwell Virginia received numerous batches of unfortunate wretches that paid for their hostility to Parliament with banishment and servitude. Not only soldiers from King Charles' army, but many captives taken in the Scotch and Irish wars were sent to the colony. On the other hand after the Restoration, hundreds of Cromwell's soldiers were sold as servants. If we estimate the annual importation of servants at 1200, the entire increase of population which Fiske notes is at once accounted for. Moreover, the mortality that in the earlier years had been so fatal to the newcomers, was now greatly reduced owing to the introduction of Peruvian bark and to the precautions taken by planters to prevent disease on their estates. Governor Berkeley said in 1671 that not many hands perished at that time, whereas formerly not one in five escaped the first year.