With the reign of Henry II. a new era opens as regards the documentary history of our ancient castles, because the Pipe Rolls of that king’s reign have most fortunately been preserved.[1164] These contain the sheriff’s accounts for money spent on the building or repair of the king’s castles, and are simply invaluable for the history of castle architecture. The following is a list of the keeps which the Pipe Rolls show to have been built or finished by Henry II.:—

Scarborough, built between 1157 and 1174.Tower
Windsor,""1161"1177.Shell wall
Orford,""1165"1172.Tower
Bridgenorth,""1166"1173.Tower
Newcastle,""1167"1177.Tower
Bowes,""1171"1187.Tower
Richmond,""1171"1174.Tower
Chilham,""1171"1173.Tower
Peak,""1172"1176.Tower
Canterbury,""1172"1174.Tower
Arundel,""1176"1182.Shell wall
Tickhill,""1178"1181.Tower

The dates given here must be taken as only roughly accurate, as owing to the meagreness of the entries in the Pipe Rolls, it is not always certain whether the expenses were for the great tower or for other buildings. The list by no means includes all the work which Henry II. did on his English castles, for he was a great builder; but a good deal of his work seems to have been the substitution of stone walls with mural towers, for wooden stockades, and our list comprises all the cases in which it is clear that the keep was the work of this king.[1165] We confine our attention to the keeps, because though mural towers of stone began to be added to the walls of baileys during Henry II.’s reign (a detail which must have greatly altered the general appearance of castles), it is certain that the keep was still the most important part, and the residence of the king or noble whenever he visited the castle.

Seven out of the ten tower keeps are built on precisely the same plan as those of Henry I. The chief advance is in the masonry. All the tower keeps of Henry II., except Dover, Chilham, and Canterbury, are or have been cased with good ashlar, of stones somewhat larger in size than those used by Henry I. The same may be said of the shell walls (namely, Windsor and Arundel); it is interesting to note that Henry II. still used this elementary form of citadel, which consisted merely of a wall round the top of a motte, with wooden buildings inside.[1166] In three cases out of the ten tower keeps, Newcastle, Bowes, and Richmond, the basement storey is vaulted, which does not occur in the older keeps.[1167] Yet such important castles as Scarborough, Dover, and Canterbury are without this provision against fire. None of these keeps appear to have more than three storeys above the basement.[1168] None of the entrances to the keeps (except Tickhill) have any portcullis grooves,[1169] nor any special contrivances for defence, except at Canterbury, where the entrance (on the first floor) takes two turns at right angles before reaching the hall to which it leads.[1170] There are nearly always in the keeps of Henry II. some signs of Transition Norman in the details, such as the nook shafts at the angles of the towers of Scarborough and the Peak, certain arches at Canterbury, the Transition capitals used at Newcastle, and the filleted string round the outside of Bowes.

But we have yet to speak of three keeps of Henry II.’s reign which are on a different plan to all the others, and which point to coming changes—Chilham, Orford, and Tickhill.[1171] Chilham is an octagonal tower of three storeys, with a square annexe on one side, which appears to be original. Orford is polygonal outside, round inside. Orford indeed is one of the most extraordinary keeps to be seen anywhere, and we must regard it as an experiment, and an experiment which appears never to have been repeated.[1172] Instead of the usual Norman buttresses, this polygonal keep has three buttress towers, placed between every four of the outer faces, 22 feet wide, and 12 feet in projection.[1173] Tickhill, however, the last keep he built, is decagonal. The object of the polygonal tower was to deflect the missiles thrown from siege engines, and the round tower was evidently considered an improvement on the polygonal for this purpose, as it subsequently supplanted the polygonal type. It is therefore rather remarkable that Henry II. built both these keeps in the second decade of his reign, and afterwards went on building square keeps like his predecessors. We have seen, however, that he built at least one polygonal tower in Normandy, that of Gisors. We must bear in mind that the Norman and Angevine frontier was the theatre of the continuous struggle of Henry II. with the French kings, Louis VII. and Philip Augustus, and that it is here that we must expect the greatest developments in military architecture.

Speaking generally, we may say that just as there was comparatively little change in armour during the 12th century until the end of Henry II.’s reign, so there was comparatively little change in military architecture during the same period. But great changes took place towards the end of the 12th century. One of these changes was a great improvement in missile engines; the trébuchet was one of the most important of these. It could throw much heavier stones than the largest catapult, and could take a more accurate aim.[1174] These new engines were useful for defence as well as attack, and this affected the architecture of castles, because flat roofs covered with lead, on which machines could be placed, were now substituted for the former sloping roofs.[1175] There are several payments for lead for roofing castles in the Pipe Rolls of Henry II., the earliest being in 1166. In the reigns of John and Henry III. the mention of lead for roofing becomes much more frequent.[1176]

Hitherto, in the defence of keeps, reliance had mainly been placed upon their passive strength, though not so entirely as has been commonly assumed, since it was always the practice to shoot with arrows from the battlements round the roof of the tower. But not only was the fighting strength of the keep increased by the trébuchet, but the introduction of the crossbow gave it a defensive arm of the greatest importance. The crossbow had been known to the Romans, and was used in the early part of the 12th century, but it was forbidden by the second Lateran Council in 1139 as a weapon hateful to God.[1177] This prohibition seems actually to have been effective, as William the Breton says expressly that the crossbow was unknown to the French before the wars of Richard I. and Philip Augustus.[1178] Richard learned the use of it in the third crusade.[1179] But to use the crossbow in the defence of buildings it was necessary to construct special loopholes for shooting, splayed downwards externally, so that it was possible to aim from them. Up till this time the loopholes of castles had been purely for light and not for shooting; anyone may see that it is impossible to take aim through an immensely thick wall unless there is a downward splay to increase the field of vision. William the Breton tells us that Richard built windows for crossbows to his towers, and this is the first mention we have of them.[1180]

From this time defensive loopholes become common in castles, and take various fanciful forms, as well as the commoner ones of the circle, square, or triangle at the base of the loop. The cross loophole, which does not appear till the latter quarter of the 13th century, is explained by Viollet le Duc as an ingenious way of allowing three or four archers to fire in a volley.[1181] But up to the present time very little study has been given to this subject, and we must be content to leave the question for future observation to settle.[1182]

The crossbowmen not only required splayed loopholes, but also niches, large enough to accommodate at least three men, so that a continuous discharge of darts (quarrells) might be kept up. Any defensive loop which really means work will have a niche like this behind it. These niches had the defect of seriously weakening the wall.

Another innovation introduced by Richard I. was that of stone machicolations, or hurdicia.[1183] Whether wooden galleries round the tops of walls, with holes for dropping down stones, boiling-water, or pitch on the heads of the besiegers had not been used from the earliest times, is regarded by Köhler as extremely doubtful.[1184] They were certainly used by the Romans, and may even be seen clearly figured on the Assyrian monuments. In the Bayeux Tapestry, the picture of Bayeux Castle shows the stockade on top of the motte crested with something extremely like hurdicia. Yet the writer has found no authentic mention of them before the end of the 12th century.[1185] The stone machicolations built by Richard round his keep of Chateau Gaillard are of an unusual type, which was only rarely imitated.[1186] But from this time wooden hurdicia became universal, to judge from the numerous orders for timber for hoarding castles and town walls in the Close Rolls of the first half of the 13th century. Towards the middle of the 13th century stone brackets for the support of wooden hurdicia began to be used; they may still be seen in the great keep of Coucy, which was begun in 1230. But machicolations entirely of stone, supported on double or triple rows of brackets, do not become common till the 14th century.[1187]