In February or March, 1166, was compiled the return of military fiefs and tenants in chief, known as the _Liber Niger_, and which professes to represent the feudal military force of the kingdom, though so far only as the division of the land into military fees was then completed. The _Liber Ruber_ states the fees, in the reign of Richard I., to have been 32,000. Orderic gives them at nearly double this, or 60,000. But there are no data for estimating, with any approach to correctness, the force that the King could bring into the field. Under Henry I. and Stephen, mercenaries were largely employed, drawn mainly from Flanders. The _Liber Niger_ has received very valuable attention at the hands of Mr. Eyton and Professor Stubbs. Early in Lent in this year Henry embarked at Southampton for Normandy, where he reduced the castles of Alençon and La Roche Mabile, and received a visit from the King of Scotland. Late in the year Geoffrey de Mandeville and Richard de Lacy engaged in an unsuccessful expedition into North Wales, and again strengthened Basingwerk Castle, during which they were attacked by the Welsh. Henry remained absent in Normandy, Gascony, and Brittany about four years, landing at Portsmouth in March, 1170; but he returned to Normandy in June. In October he wrote to Prince Henry, directing him to restore the honour of Saltwood to the Archbishop. On the 29th of December, Becket was murdered, the assassins having rested at Saltwood the preceding night. After the murder they went to Knaresborough Castle, then held by Hugh de Morville as castellan. In August, 1171, Henry landed at Portsmouth, and early in September was in South Wales, where he took Caerleon from Iorwerth ap Owen, and went on to Pembroke Castle to meet Prince Rhys, to whom he made over a large part of Cardigan. From Pembroke, or rather from Milford, he went, in October, to Ireland, whence he returned, by St. David’s and by Cardiff, to England in April, 1172, and thence embarked from Portsmouth for the Continent in May. In April, 1173, the confederacy between the King of France and Prince Henry, who carried with him the discontented party among the English barons, broke out into open war in both countries. Henry the elder remained at Rouen, and with the doubtful exception of a short visit to England was content to leave the conduct of the war there to the faithful and able Richard de Lacy.