The whole Protestant world was defied by the persecution of the Huguenots which was to culminate in the revocation of the Edict of Nantes. In the mind of Lewis peace meant a series of outrages on the powers around him; but every outrage helped the cool and silent adversary who was looking on from the Hague to build up that Great Alliance of all Europe from which alone he looked for any effectual check to the ambition of France. The experience of the last war had taught William that of such an alliance England must form a part, and the efforts of the Prince ever since the peace had been directed to secure her co-operation. A reconciliation of the King with his Parliament was an indispensable step towards freeing Charles from his dependence on France, and it was such a reconciliation that William at first strove to bring about; but he was for a long time foiled by the steadiness with which Charles clung to the power whose aid was needful to carry out the schemes which he was contemplating. The change of policy however which followed on the fall of the Cabal and the entry of Danby into power raised new hopes in William's mind; and his marriage with Mary dealt Lewis what proved to be a fatal blow.
James was without a son, and the marriage with Mary would at any rate ensure William the aid of England in his great enterprise on his father-in-law's death. But it was impossible to wait for that event, and though the Prince used his new position to bring Charles round to a decided policy his efforts remained fruitless. The storm of the Popish Plot complicated his position. In the earlier stages of the Exclusion Bill, when the Parliament seemed resolved simply to pass over James and to seat Mary at once on the throne after her uncle's death, William stood apart from the struggle, doubtful of its issue, though prepared to accept the good luck if it came to him. But the fatal error of Shaftesbury in advancing the claims of Monmouth forced him into action. To preserve his wife's right of succession, with all the great issues which were to come of it, no other course was left than to adopt the cause of the Duke of York. In the crisis of the struggle, therefore, William threw his whole weight on the side of James. The eloquence of Halifax secured the rejection of the Exclusion Bill, and Halifax was but the mouthpiece of William.
But while England was seething with the madness of the Popish Plot and of the royalist reaction, the great European struggle was drawing nearer and nearer. The patience of Germany was worn out by the ceaseless aggressions of Lewis, and in 1686 its princes had bound themselves at Augsburg to resist all further encroachments on the part of France. From that moment war became inevitable, and William watched the course of his father-in-law with redoubled anxiety. His efforts to ensure English aid had utterly failed. James had renewed his brother's secret treaty with France, and plunged into a quarrel with his people which of itself would have prevented him from giving any aid in a struggle abroad. The Prince could only silently look on, with a desperate hope that James might yet be brought to a nobler policy. He refused all encouragement to the leading malcontents who were already calling on him to interfere in arms. On the other hand he declined to support the King in his schemes for the abolition of the Test. If he still cherished hopes of bringing about a peace between the King and people which might enable him to enlist England in the Grand Alliance, they vanished in 1687 before the Declaration of Indulgence. It was at this moment that James called on him to declare himself in favour of the abolition of the penal laws and of the Test. But simultaneously with the King's appeal came letters of warning and promises of support from the leading English nobles.
Some, like the Hydes, simply assured him of their friendship. The Bishop of London added promises of support. Others, like Devonshire, Nottingham, and Shrewsbury, cautiously or openly warned the Prince against compliance with the King's demand. Lord Churchill announced the resolve of Mary's sister Anne to stand by the cause of Protestantism. Danby, the leading representative of the great Tory party, sent urgent warnings. The letters dictated William's answer. No one, he truly protested, loathed religious persecution more than he himself did, but in relaxing political disabilities James called on him to countenance an attack on his own religion. "I cannot," he ended, " concur in what your Majesty desires of me." But Will.am still shrank from the plan of an intervention in arms. General as the disaffection undoubtedly was, the position of James seemed fairly secure. He counted on the aid of France. He had an army of twenty thousand men. Scotland, disheartened by the failure of Argyll's rising, could give no such aid as it gave to the Long Parliament. Ireland was ready to throw a Catholic army on the western coast. It was doubtful if in England itself disaffection would turn into actual rebellion.
The "Bloody Circuit" had left its terror on the Whigs. The Tories and the Churchmen, angered as they were, were hampered by their doctrine of non-resistance. William's aim therefore was to discourage all violent counsels, and to confine himself to organizing such a general opposition as would force James by legal means to reconcile himself to the country, to abandon his policy at home and abroad, and to join the alliance against France.
But at this moment the whole course of William's policy was changed by an unforeseen event. His own patience and that of the nation rested on the certainty of Mary's succession. But in the midst of the King's struggle with the Church it was announced that the Queen was again with child. The news was received with general unbelief for five years had passed since the last pregnancy of Mary of Modena. But it at once forced on a crisis. If, as the Catholics joyously foretold, the child turned out a boy, and, as was certain, was brought up a Catholic, the highest Tory had to resolve at last whether the tyranny under which England lay should go on for ever. The hesitation of the country was at an end. Danby, loyal above all to the Church and firm in his hatred of subservience to France, answered for the Tories; Compton for the High Churchmen, goaded at last into rebellion by the Declaration of Indulgence. The Earl of Devonshire, the Lord Cavendish of the Exclusion struggle, answered for the Nonconformists, who were satisfied with William's promise to procure them toleration, as well as for the general body of the Whigs. The announcement of the birth of a Prince of Wales was followed ten days after by a formal invitation to William to intervene in arms for the restoration of English liberty and the protection of the Protestant religion; it was signed by the representatives of the great parties now united against a common danger, and by some others, and was carried to the Hague by Herbert, the most popular of English seamen, who had been deprived of his command for a refusal to vote against the Test. The Invitation called on William to land with an army strong enough to justify those who signed it in rising in arms.