Granting of land was again used on a large scale for the establishment of forts after the Indian massacre of 1644. By order of the Assembly in 1645 blockhouses or forts were established at strategic points: Fort Charles at the falls of the James River, Fort Royal at Pamunkey, Fort James on the ridge of Chickahominy on the north side of the James, and in the next year Fort Henry at the falls of the Appomattox River. The maintenance of these forts involved considerable expense, more than the officials of the colony wished to drain from the public treasury. Therefore, they decided to grant the forts with adjoining lands to individuals who would accept the responsibility of their upkeep as well as the maintenance of an adequate force for defense. Fort Henry, located at present-day Petersburg, was granted to Captain Abraham Wood with 600 acres of land plus all houses, edifices, boats, and ammunition belonging to the fort. Wood was required to maintain and keep ten persons continuously at the fort for three years. During this time he was exempted from all public taxes for himself and the ten persons. Upon similar terms Lieutenant Thomas Rolfe, son of Pocahontas and John Rolfe, received Fort James and 400 acres of land; Captain Roger Marshall, Fort Royal and 600 acres. Since there was no arable land adjoining Fort Charles at present-day Richmond, other inducements were made for its maintenance. These forts served as the first line of defense against possible attacks by the natives. Being the center of the varied activities of the frontier, they also were the starting point for expeditions against the Indians and became the center of trade for the outlying regions. The fourth condition for granting of land--the headright--was by far the most important and became the principal basis for title to land in the seventeenth century. Its origin goes back to "the greate charter" of 1618 in which the following provision was included: That for all persons ... which during the next seven years after Midsummer Day 1618 shall go into Virginia with intent there to inhabite If they continue there three years or dye after they are shiped there shall be a grant made of fifty acres for every person upon a first division and as many more upon a second division (the first being peopled) which grants to be made respectively to such persons and their heirs at whose charges the said persons going to inhabite in Virginia shall be transported with reservation of twelve pence yearly rent for every fifty acres to be answered to the said treasurer and company and their successors for ever after the first seven years of every such grant.