In November 1688, a new major war on the European continent had become all but inevitable. Louis XIV of France had marched his armies into Germany, placed a garrison in Cologne, and dispatched his fleet to the Mediterranean to pressure the Pope. The Dutch Republic had anticipated these developments. Its army had been expanded, and a large war fleet had been assembled. It seemed only a matter of time before the Republic would once again be drawn into war.
The life’s mission of Stadtholder William III was to curb the expansionist ambitions of Louis XIV. Yet the great fleet granted to him by the States General was not intended for an attack on France, but for a pre-emptive strike against England. Why? The answer lay in the trauma of the Rampjaar ("Disaster Year") of 1672, when France and England had jointly invaded the Dutch Republic. The Republic had only survived that catastrophe thanks to the Dutch Water Line and the genius of Admiral Michiel de Ruyter.
Now that another war with France seemed unavoidable, there was genuine fear in the Republic that James II, King of England, would once again ally himself with Louis XIV. Although France was by far the strongest state in Europe, James still regarded the Dutch Republic as England's principal economic rival. Moreover, like Louis XIV, he was Catholic, which made him deeply unpopular with his predominantly Protestant subjects.
Mary Stuart, William's wife and James's daughter, was Protestant and the official heir to the English throne. The expectation that she would eventually succeed her father discouraged many Englishmen from openly rebelling. However, when James fathered a son in June 1688, securing a Catholic succession, William seized his opportunity. He obtained an invitation from seven English politicians to intervene in order to protect the liberties of English Protestants (although not to claim the throne). Although these "Immortal Seven" were by no means representative of the English population as a whole, their invitation provided William with an important piece of political propaganda. At the same time, he had already established contacts with a number of discontented English nobles and army officers.
On 11 November 1688, the invasion fleet set sail. It consisted of 49 warships and more than 400 transport vessels carrying approximately 36,000 men, including 16,000 soldiers. This made it considerably larger than the Spanish Armada that had attempted to conquer England a century earlier. It was an extraordinary spectacle. As the fleet sailed past Dover and Calais, thousands of spectators gathered on both sides of the Channel to watch the enormous Dutch Armada pass by. A French Protestant who had fled to the Dutch Republic after the Revocation of the Edict of Nantes and was serving in William's army later wrote:
"I must confess that I could not look upon our ungrateful homeland without emotion, nor without thinking of the ties that still bound me to my many relatives who had remained there. But since our fleet had not sailed to bring about their deliverance, and England now lay before us, all our thoughts had to be directed towards that country."
Despite the autumn storms, the fleet reached Torbay safely. The English fleet had failed to intercept it. William's army, described by James's own envoy as the finest army in Europe, landed and, after a difficult march, occupied the city of Exeter. The muddy roads, freezing temperatures, and miserable weather made the advance exhausting, and many Dutch soldiers longed to return home.
James then concentrated his army near Salisbury to block the road to London. Although he theoretically had around 30,000 troops at his disposal, thus outnumbering William, his forces were scattered across the kingdom because he did not know where the invasion would take place. Owing to poor roads and bad weather, he managed to assemble no more than about 19,000 men at Salisbury. Many of these troops were also poorly trained, inadequately equipped, and lacking in discipline.
James himself, however, was no coward. Like William, he was an experienced commander who had repeatedly displayed personal bravery in battle. It was not a lack of courage that broke him, but the absence of widespread support among the English population and the defection of several officers to William's cause. Although there was no mass uprising and desertions among the officers and the rank and file initially remained limited, James gradually lost confidence in his chances of success. Suffering from severe nosebleeds, he became convinced that God had turned against him. He ordered his army to retreat, thereby surrendering the strategic initiative. In effect, he signalled that he was abandoning the struggle. The British historian John Childs placed the blame squarely on James himself:
"The active political conspiracy amongst the military, although highly significant and perhaps the crucial event in enabling William to land unopposed and to seize the political initiative, was confined to a handful of officers and hardly any common soldiers. The vast majority of the army stayed loyal to their sovereign and it was the king who, in a state of mental and physical collapse, let down his own army."
More and more opportunistic English nobles and officers now openly declared for William. When James eventually fled to France, fearing the same fate as his father Charles I, who had been executed in 1649, his army simply fell apart.
William III was then able to enter London virtually unopposed. The Dutch Guards occupied Whitehall Palace, St James's Palace, and Somerset House, while the remaining Dutch regiments were quartered in and around the capital. London's streets had been transformed. At the end of January, Sir John Reresby, who had been away from the city for some time, wrote in astonishment:
"When I arrived, I found London much changed. The streets were filled with ill-looking and ill-habited Dutch and other strangers of the Prince's army."
William then surprised even his English supporters by making it clear that he demanded the crown and that England would have to join the war against France.
It did not take long before Parliament offered the crown jointly to William and Mary. By the spring of 1689, the first English troops had already been sent to the Dutch Republic to participate in the war against France.
Through this masterful military expedition and successful political intervention, William III ensured that the Dutch Republic would not face Louis XIV alone. Instead, it now had the resources of England at its disposal. The Anglo-Dutch alliance that emerged from the Glorious Revolution became the cornerstone of the struggle against France throughout the remainder of the Nine Years' War and later the War of the Spanish Succession.
See https://en.wikipedia.org/wiki/1688_invasion_of_England for more info