During his residence in Oxford he displayed a temper usually grave, and in appearance morose, but inclined at times and with particular friends to be very cheerful, though still with a tincture of severity that disposed him to bear hard upon the pride of courtiers and the powers of churchmen; which rendered him very agreeable company to the good fellows of those days. This is certain, that his reputation for probity and his known aversion to persecution caused the Puritans to promote his election as a burgess for Bridgewater in the parliament which sat in April 1640. This assembly was dissolved too early for Blake to make any discovery therein of his talents as a senator; and in the long parliament, which sat soon after, he lost his election. When the war broke out between the king and the parliament he declared for the latter, and took arms very early in their service; but where, and in what capacity, is not very clear. However, he was very soon made a captain of dragoons, in which position he showed himself as able and active an officer as any in the service; and as such was constantly employed upon occasions when boldness or dexterity were requisite. In 1643 he was at Bristol, under the command of Colonel Fiennes, who entrusted him with a little fort on the line, in which he first gave the world a proof of his military prowess; for, on July 26th, when Prince Rupert attacked that important place, and the governor had agreed to surrender it upon articles, Blake still held out his fort and killed several of the king's forces. This exasperated Prince Rupert to such a degree that he talked of hanging him, and would probably have carried out his threat had not some friends interposed and excused the young officer on account of his want of experience in war, and then prevailed upon him to give up the fort. After this Blake served in Somersetshire under the command of Popham, who was governor of Lyme, to whose regiment he was lieutenant-colonel. While here, in conjunction with Sir Robert Pye, he surprised Taunton for the parliament, capturing ten pieces of cannon and a great deal of ammunition. In 1664 he was made governor of the town, an important appointment, as Taunton contained the only garrison the parliament had in the west. The works about it, however, were far from being strong, and the garrison was by no means numerous; yet by keeping a strict discipline, and treating the townsmen well, he made shift to keep it, though no great care was taken to furnish him with supplies, and he was often besieged and blocked up by the king's forces.