Cromwell's policy in this instance was not overturned at the Restoration, and the great Jewish immigration into England with all its important consequences may be held to date practically from these first concessions made by Cromwell. His personal intervention also alleviated the condition of the Quakers, much persecuted at this time. In an interview in 1654 the sincerity and enthusiasm of George Fox had greatly moved Cromwell and had convinced him of their freedom from dangerous political schemes. He ordered Fox's liberation, and in November 1657 issued a general order directing that Quakers should be treated with leniency, and be discharged from confinement. Doctrines directly attacking Christianity Cromwell regarded, indeed, as outside toleration and to be punished by the civil power, but at the same time he mitigated the severity of the penalty ordained by the law. In general the toleration enjoyed under Cromwell was probably far larger than at any period since religion became the contending ground of political parties, and certainly greater than under his immediate successors. Lilburne and the anabaptists, and John Rogers and the Fifth Monarchy men, were prosecuted only on account of their direct attacks upon the government, and Cromwell in his broad-minded and tolerant statesmanship was himself in advance of his age and his administration. He believed in the spiritual and unseen rather than in the outward and visible unity of Christendom.
In foreign policy Cromwell's chief aims appear to have been to support and extend the Protestant faith, to promote English trade, and to prevent a Stuart restoration by foreign aid--the religious mission of England in the world, her commercial interests, and her political independence being indissolubly connected in his mind. The beginning of his rule inherited a war with France and Holland; the former consequent on Cromwell's failure to obtain terms for the Huguenots or the cession of Dunkirk, and the latter--for which he was not responsible--the result of commercial rivalry, of disputes concerning the rights of neutrals, of bitter memories of Dutch misdeeds in the East Indies, and of dynastic causes arising from the stadtholder, William II. of Orange, having married Mary, daughter of Charles I. In 1651 the Dutch completed a treaty with Denmark to injure English trade in the Baltic; to which England replied the same year by the Navigation Act, which suppressed the Dutch trade with the English colonies and the Dutch fish trade with England, and struck at the Dutch carrying trade. War was declared in May 1652 after a fight between Blake and Tromp off Dover, and was continued with signal victories and defeats on both sides till 1654. The religious element, however, which predominated in Cromwell's foreign policy inclined him to peace, and in April of that year terms were arranged by which England on the whole was decidedly the gainer. The Dutch acknowledged the supremacy of the English flag in the British seas, which Tromp had before refused; they accepted the Navigation Act, and undertook privately to exclude the princes of Orange from the command of their forces. The Protestant policy was further followed up by treaties with Sweden and Denmark which secured the passage of the Sound for English ships on the same conditions as the Dutch, and a treaty with Portugal which liberated English subjects from the Inquisition and allowed commerce with the Portuguese colonies. The two great Roman Catholic powers now both bid for Cromwell's alliance. Cromwell wisely inclined towards France, for Spain was then a greater menace than France alike to the Protestant cause and to the growth of British trade in the western hemisphere; but as no concessions could be gained from either France or Spain, the year 1654 closed without a treaty being made with either. In December 1654 Penn and Venables sailed for the West Indies with orders to attack the Spanish colonies and the French shipping; and for the first time since the Plantagenets an English fleet appeared in the Mediterranean, where Blake upheld the supremacy of the English flag, made a treaty with the dey of Algiers, destroyed the castles and ships of the dey of Tunis at Porto Farina on the 4th of April 1655, and liberated the English prisoners captured by the pirates.