gunpowder weaponry fundamentally altered the nature of castle architecture from the mid-fifteenth century, with existing castles being adapted to allow the use of gunpowder weapons by the incorporation of "keyhole" gun ports, platforms to mount guns and walls being modified to resist bombardment. ravenscraig, kirkcaldy, begun about 1460, is probably the first castle in the british isles to be built as an artillery fort, incorporating "d-shape" bastions that would better resist cannon fire and on which artillery could be mounted. in the period of french intervention in the 1540s and 1550s, at the end of the rough wooing, scotland was given a defended border of a series of earthwork forts and additions to existing castles. these included the erection of single bastions at edinburgh, stirling and dunbar; the creation of the scots' dike on the western end of the border; trace italienne fortresses at leith, inchkeith and langholm; work was also begun at jedburgh and plans made for works at kelso. the most aggressive move was a fortified artillery park at eyemouth, only from the english border stronghold of berwick.