Lambert, born at Gallon Hall, Kirkby Malham, in the West Riding of Yorkshire, of a long-established family, studied law at the Inns of Court in London. In 1639 he married Frances, daughter of Sir William Lister.
In September 1642, Lambert was appointed a captain of horse in the army commanded by Ferdinando, Lord Fairfax. Within a year, he was colonel of a cavalry regiment, and distinguished himself at the siege of Hull in October, 1643. Early in 1644 he did good service at the battles of Nantwich and Bradford. At Marston Moor (2 July 1644) Lambert's own regiment was routed by the charge of Goring's horse; but he cut his way through with a few troops and joined Cromwell on the other side of the field.
When the New Model Army formed in the beginning of 1645, Colonel Lambert was appointed to succeed Sir Thomas Fairfax in command of the northern forces, with the title of commissary-general. He was soon replaced by Sydnam Poyntz, and under this officer he served in the Yorkshire campaign of 1645, receiving a wound before Pontefract. In 1646 he was given a regiment in the New Model, serving with Sir Thomas Fairfax in the west of England, and he was a commissioner, with Cromwell and others, for the surrender of Oxford in the same year. "It is evident", says C. H. Firth (in the Dictionary of National Biography), "that he was from the first regarded as an officer of exceptional capacity and specially selected for semi-political employments".
When the quarrel between the army and parliament began, Lambert supported the army's cause. He assisted Ireton in drawing up the addresses and remonstrances issued by the army, both men having had some experience in law. Early in August 1647 Lambert was sent by Fairfax as major-general to take charge of the forces in the northern counties. His management of affairs in those parts is praised by Whitelocke. He suppressed a mutiny among his troops, kept strict discipline and hunted down the moss-troopers who infested the moorland country.
When the Scottish army under the James Hamilton, 1st Duke of Hamilton invaded England in the summer of 1648, Lambert was engaged in suppressing the Royalist rising in his district. The arrival of the Scots obliged him to retreat; but Lambert continued to harass the invaders till Cromwell came up from Wales and the Scottish army was destroyed in the three days' fighting from Preston to Warrington. After the battle Lambert's cavalry headed the chase, pursuing the defeated army, and finally surrounded it at Uttoxeter, where Hamilton surrendered to Lambert on August 25, 1648. Lambert then led the advance of Cromwell's army into Scotland, where he was left in charge on Cromwell's return. From December 1648 to March 1649 he was engaged in the successful siege of Pontefract Castle; Lambert was thus absent from London at the time of Pride's Purge and the trial and execution of King Charles I.
When Cromwell was appointed to the command of the war in Scotland (July 1650), Lambert went with him as major-general and second in command. He was wounded at Musselburgh, but returned to the front in time to take a conspicuous share in the victory of Dunbar. He himself defeated the "Protesters" or "Western Whigs" at Hamilton on 1 December 1650. In July 1651 he was sent into Fife to get in the rear and flank of the Scottish army near Falkirk, and force them to decisive action by cutting off their supplies. This mission, in the course of which Lambert won an important victory at Inverkeithing, was so successful that Charles II, as Lambert had foreseen, made for England. Lambert's part in the general plan of the resulting Worcester campaign was carried out brilliantly, and in the crowning victory of Worcester he commanded the right wing of the English army, and had his horse shot under him. Parliament granted him lands in Scotland worth £1000 per annum.
In October 1651 Lambert was made a commissioner to settle the affairs of Scotland, and on the death of Ireton he was appointed lord deputy of Ireland (January 1652). He made extensive preparations; parliament, however, reconstituted the Irish administration and Lambert refused to accept office on the new terms. He then began to oppose the Rump Parliament. In the council of officers he headed the party desiring representative government, as opposed to Harrison who favoured an oligarchy of "God-fearing" men, but both hated what remained of the Long Parliament, and joined in urging Cromwell to dissolve it by force.
At the same time Lambert was consulted by the parliamentary leaders as to the possibility of dismissing Cromwell from his command, and on March 15, 1653 Cromwell refused to see him, speaking of him contemptuously as "bottomless Lambert". On April 20, 1653, however, Lambert accompanied Cromwell when he dismissed the council of state, on the same day as the forcible expulsion of the parliament.
Lambert now favoured the formation of a small executive council, to be followed by an elective parliament whose powers should be limited by a written instrument of government. As the ruling spirit in the council of state, and the idol of the army, he was seen as a possible rival of Cromwell for the chief executive power, while the royalists for a short time had hopes of his support. He was invited, with Cromwell, Harrison and John Desborough, to sit in the nominated "Barebones Parliament" of 1653; and when the unpopularity of that assembly increased, Cromwell drew nearer to Lambert. In November 1653 Lambert presided over a meeting of officers, when the question of constitutional settlement was discussed, and a proposal made for the forcible expulsion of the nominated parliament. On December 12, 1653, the parliament resigned its powers into Cromwell's hands, and on December 13 Lambert obtained the consent of the officers to the Instrument of Government, in the framing of which he had taken a lead. He was one of the seven officers nominated to seats in the council created by the Instrument.
In the foreign policy of the Protectorate Lambert called for alliance with Spain and war with France in 1653, and he firmly withstood Cromwell's design for an expedition to the West Indies. In the debates in parliament on the Instrument of Government in 1654 Lambert proposed that the office of Lord Protector should be made hereditary, but was defeated by a majority which included members of Cromwell's family. In the parliament of this year, and again in 1656, Lord Lambert, as he was now styled, sat as member for the West Riding. He was one of the major-generals appointed in August 1655 to command the militia in the ten districts into which it was proposed to divide England, and who were to be responsible for the maintenance of order and the administration of the law in their several districts.
Lambert took a prominent part in the committee of council which drew up instructions to the major-generals. He was the organiser of the system of police which these officers were to control. Gardiner conjectures that it was through divergence of opinion between the protector and Lambert in connection with these "instructions" that the estrangement between the two men began. At all events, although Lambert had himself at an earlier date requested Cromwell to take the royal dignity, when the proposal to declare Oliver king was started in parliament (February 1657) he at once opposed it.
A hundred officers headed by Fleetwood and Lambert waited on the protector, and begged him to put a stop to the proceedings. Lambert was not convinced by Cromwell's arguments, and their complete estrangement, personal as well as political, followed. On his refusal to take the oath of allegiance to the protector, Lambert was deprived of his commissions, receiving instead a pension of £2000 a year. He retired from public life to Wimbledon; but shortly before his own death Cromwell sought a reconciliation, and Lambert and his wife visited Cromwell at Whitehall.
When Richard Cromwell was proclaimed protector (3 September 1658), his chief difficulty lay with the army, over which he exercised no effective control. Lambert, though holding no military commission, was the most popular of the old Cromwellian generals with the rank and file of the army, and it was very generally believed that he would install himself in Oliver Cromwell's seat of power. Richard Cromwell's adherents tried to conciliate him, and the royalist leaders made overtures to him, even proposing that Charles II should marry Lambert's daughter. Lambert at first gave a lukewarm support to Richard Cromwell, and took no part in the intrigues of the officers at Fleetwood's residence, Wallingford House. He was a member of the parliament which met in January 1659, and when it was dissolved in April under compulsion of Fleetwood and Desborough, he was restored to his commands. He headed the deputation to Lenthall in May 1659 inviting the return of the Rump, which led to the tame retirement of Richard Cromwell; and he was appointed a member of the committee of safety and of the council of state.
When the parliament, in an attempt to control the power of the army, withheld from Fleetwood the right of nominating officers, Lambert was named one of a council of seven charged with this duty. The parliament's evident distrust of the soldiers caused much discontent in the army; while the absence of authority encouraged the royalists to make overt attempts to restore Charles II, the most serious of which, under Sir George Booth and the earl of Derby, was crushed by Lambert near Chester on August 19, 1659. He promoted a petition from his army that Fleetwood might be made lord-general and himself major-general. The republican party in the House took offence. The Commons (October 12, 1659) cashiered Lambert and other officers, and retained Fleetwood as chief of a military council under the authority of the speaker. On the next day Lambert caused the doors of the House to be shut and the members kept out. On October 26, a "committee of safety" was appointed, of which he was a member. He was also appointed major-general of all the forces in England and Scotland, Fleetwood being general.
Lambert was now sent with a large force to meet Monck, who was in command of the English forces in Scotland, and either negotiate with him or force him to terms. Monck, however, marched southward. Lambert's army began to melt away, and he was kept in suspense by Monck till his whole army deserted and he returned to London almost alone. Monck marched to London unopposed. The excluded Presbyterian members were recalled. Lambert was sent to the Tower (March 3, 1660), from which he escaped a month later. He tried to rekindle the civil war in favour of the Commonwealth, but was speedily recaptured and sent back to the Tower (April 24, 1660).
On the Restoration Lambert was exempted from danger of life by an address of both Houses to the king, but the next parliament (1662) charged him with high treason. For the rest of his life, Lambert remained in custody in Guernsey. Lambert's role in the Civil War and Commonwealth is now largely forgotten.
It has been said that Lambert's nature had more in common with the royalist than with the puritan spirit. Vain and ambitious, he believed that Cromwell could not stand without him; and when Cromwell was dead, he imagined himself entitled to succeed him. As a soldier he was far more than a fighting general and possessed many of the qualities of a great general. He was an able writer and speaker, and an accomplished negotiator and took pleasure in quiet and domestic pursuits. He learnt his love of gardening from Lord Fairfax, who was also his master in the art of war. He painted flowers, besides cultivating them, and was accused by Mrs Hutchinson of "dressing his flowers in his garden and working at the needle with his wife and his maids". It has been said that he became a Roman Catholic before his death.
Text updated from 1911 Encyclopaedia Britannica