That of 1703 was marred even more effectually than that of the previous year by the interference of the deputies, and the ill-concealed opposition to Marlborough of certain Dutch generals, notably of Slangenburg.  The duke was very angry, and bitter recriminations ensued.  In the end Slangenburg was removed from his command; and the appointment of Ouwerkerk, as field-marshal of the Dutch forces, relieved the tension, though the deputies were still present at headquarters, much to Marlborough’s annoyance.  The campaign resulted in the capture of Bonn, Huy and Limburg, but there was no general action.

The year 1704 saw the genius of Marlborough at length assert itself.  The French had placed great armies in the field, Villeroy in the Netherlands, Tallard in Bavaria, where in conjunction with the Bavarian forces he threatened to descend the Danube into the heart of Austria.  Vienna itself was in the greatest danger.  The troops under Lewis of Baden and under Eugene were, even when united, far weaker than their adversaries.  In these circumstances Marlborough determined by a bold strategical stroke to execute a flank march from the Netherlands right across the front of the Franco-Bavarian army and effect a junction with the Imperialists.  He had to deceive the timid Dutch deputies by feigning to descend the Meuse with the intention of working round Villeroy’s flank; then, leaving Ouwerkerk to contain that marshal, he set out on his daring adventure early in May and carried it out with complete success.  His departure had actually relieved the Netherlands, for Villeroy had felt it necessary with a large part of his forces to follow Marlborough and reinforce the Franco-Bavarians under Marshal Tallard and the Elector.  The two armies met at Blenheim (Hochstaedt) on August 13.  The battle resulted in the crushing victory of the allies under Marlborough and Eugene.  Eleven thousand prisoners were taken, among them Tallard himself.  The remnant of the French army retired across the Rhine.  Vienna was saved, and all Bavaria was overrun by the Imperialists.

Meanwhile at sea the Anglo-Dutch fleet was incontestably superior to the enemy; and the operations were confined to the immediate neighbourhood of the Peninsula.  William III had before his death been preparing an expedition for the capture of Cadiz.  His plan was actually carried out in 1702, when a powerful fleet under the supreme command of Admiral Sir George Rooke sailed for Cadiz; but the attack failed owing to the incompetence of the Duke of Ormonde, who commanded the military forces.  In this expedition a strong Dutch squadron under Philip van Almonde participated.  Almonde was a capable seaman trained in the school of Tromp and De Ruyter; and he took a most creditable part in the action off Vigo, October 23, in which a large portion of the silver fleet was captured, and the Franco-Spanish fleet, which formed its escort, destroyed.  The maritime operations of 1703 were uneventful, the French fleet being successfully blockaded in Toulon harbour.