His pawns were attacking the white king that had castled on the queenside. Most often the checkmated king has castled queenside, and is mated on c8 or c1. The rook is then used to support a piece attack against White's castled king. Three of his victims were castled by his yorker. The computer played book moves and they castled symmetrically to defend their kings. Within a matter of years, England was fully castled. Castled was burnt, fringe and entrance towers sustained most of the damage. Black has achieved a normal castled position (Rf8, Kg8), but in several moves. The Roman poet Virgil called it "that castled cliff, Monoecus by the sea" ("Aeneid", VI.830).