In order to defend himself against any sudden invasion, which he had cause enough to expect, he gave all men licence to build castles upon their lands, which proved a very mistaken piece of politics, although grounded upon some appearance of reason. The King supposed that no invader would venture to advance into the heart of his country without reducing every castle in his way, which must be a work of much time and difficulty, nor would be able to afford men to block them up, and secure his retreat: which way of arguing may be good enough to a prince of an undisputed title, and entirely in the hearts of his subjects: but numerous castles are ill defenders of an usurpation, being the common retreat of malcontents, where they can fly with security, and discover their affections as they please: by which means the enemy, although beaten in the field, may still preserve his footing in the bowels of a country; may wait supplies from abroad; and prolong a war for many years: nor, while he is master of any castles, can he ever be at mercy by any sudden misfortune; but may be always in a condition of demanding terms for himself. These, and many other effects of so pernicious a counsel, the King found through the whole course of his reign; which was entirely spent in sieges, revolts, surprises, and surrenders, with very few battles, but no decisive action: a period of much misery and confusion, which affords little that is memorable for events, or useful for the instruction of posterity. 1136. The first considerable enemy that appeared against him was David King of Scots, who having taken the oath of fealty to Maud and her issue, being further engaged by the ties of blood, and stirred up through the persuasions of several English nobles, began to take up arms in her cause; and invading the northern parts, took Carlisle and Newcastle; but upon the King's speedy approach with his forces, a peace was presently made, and the towns restored. However, the Scottish prince would, by no means, renounce his fidelity to the Empress, by paying homage to Stephen; so that an expedient was found to have it performed by his eldest son: in consideration of which the King gave, or rather restored, to him the Earldom of Huntingdon. Upon his return to London from this expedition, he happened to fall sick of a lethargy, and it was confidently given out that he was dead. This report was, with great industry and artifice, dispersed by his enemies, which quickly discovered the ill inclination of several lords, who, although they never believed the thing, yet made use of it for an occasion or pretext to fortify their castles, which they refused to surrender to the King himself; but Stephen was resolved, as he said, to convince them that he was alive and well; for coming against them before he was expected, he recovered Exeter, Norwich,[27] and other fortified places, although not without much difficulty. [Footnote 27: Hugh Bigod had seized Norwich Castle. [D.S.]]