Little is known of Waller's life up to 1640, when he became member of parliament for Andover. As a strict Presbyterian by religion, and a member of the opposition in politics, he naturally threw himself with the greatest ardour into the cause of the parliament when the Civil War broke out in 1642. He immediately received an appointment as a colonel, and conducted to a speedy and successful issue the siege of Portsmouth in September 1642; and later in the year captured Farnham, Winchester and other places in the south-west of England. At the beginning of 1643 Waller was made a major-general and placed in charge of operations in the region of Gloucester and Bristol, and he concluded his first campaign with a victory at Highnam and the capture of Hereford.
He was then called upon to oppose the advance of Sir Ralph Hopton and the Royalist western army, and though more or less defeated in the hard-fought battle of Lansdowne (near Bath) he shut up the enemy in Devizes. However, Hopton and a relieving force from Oxford inflicted a crushing defeat upon Waller's army at the Battle of Roundway Down (13 July 1643). Hopton was Waller's intimate personal friend, and some correspondence passed between the opposing generals, a quotation from which ( Gardiner, Civil War, i. 168) is given as illustrative of "the temper in which the nobler spirits on either side had entered on the war". Waller wrote:
Waller himself, a general of the highest skill — "the best shifter and chooser of ground" on either side - was, like Turenne, at his best at the head of a small and highly-disciplined regular army. Only a Condé or a Cromwell could have enforced discipline and soldierly spirit in such men, ill-clad and unpaid as they were, and the only military quality lacking to Wailer was precisely this supreme personal magnetism.
In these circumstances affairs went from bad to worse. Though successful in stopping Hopton's second advance at Cheriton (March 1644), he was defeated by Charles I in the war of manoeuvre which ended with the action of Cropredy Bridge (June 1644), and in the second battle of Newbury in October 1644 his tactical success at the village of Speen led to nothing. His last expeditions were made into the west for the relief of Taunton, and in these he had Cromwell as his lieutenant-general.
By this time the confusion in all the armed forces of the parliament had reached such a height that reforms were at last taken in hand. The original suggestion of the celebrated "New Model Army" came from Waller, who wrote to the Committee of Both Kingdoms (2 July 1644) to the effect that "an army compounded of these men will never go through with your service, and till you have an army merely your own that you may command, it is in a manner impossible to do anything of importance."
Simultaneously with the New Model came the Self-denying Ordinance, which required all members of parliament to lay down their military commands. Waller did so gladly - the more as he had already requested to be relieved - and his active military career came to an end. But the events of 1643 - 1644 had done more than embitter him. They had combined with his Presbyterianism to make him intolerant of all that he conceived to be licence in church, state or army, and after he ceased to exercise command himself he was constantly engaged, in and out of parliament, in opposing the Independents and the army politicians, and supporting the cause of his own religious system, and later that of the Presbyterian-Royalist opposition to the Commonwealth and Protectorate régime. He was aeveral times imprisoned between 1648 and 1659.
In the latter year Waller worked actively in promoting the final negotiations for the restoration of Charles II and reappeared in the House of Commons. He sat in the Convention Parliament, but soon retired from political life. He died on September 19 1668.
See Wood's Athenae Oxonienses, ed. Bliss, iii. 812 and two partial autobiographies, Recollections by General Sir William Waller (printed in The Poetry of Anna Matilda, 1788), and Vindication of the Character, &c. (1797).
For a modern work, see: Roundhead General: the Campaigns of Sir William Waller by John Adair ISBN 0750913126
Original text from 1911 Encyclopaedia Britannica