Prince Eugene of Savoy
'Cold war'

The 1720s saw rapidly changing alliances between the European powers and almost constant diplomatic confrontation, largely over unsolved issues regarding the Quadruple Alliance. The Emperor and the Spanish king continued to use each other's titles, and Charles VI still refused to remove the remaining legal obstacles to Don Charles' eventual succession to the duchies of Parma and Tuscany. Yet in a surprise move Spain and Austria moved closer with the signing of the Treaty of Vienna in April/May 1725. In response Britain, France, and Prussia joined together in the Alliance of Hanover to counter the danger to Europe of an Austro-Spanish hegemony. For the next three years there was the continual threat of war between the Hanover Treaty powers and the Austro-Spanish bloc.

From 1726, Eugene gradually began to regain his political influence. With his many contacts throughout Europe Eugene, backed by Gundaker Starhemberg and Count Schönborn, the Imperial vice-chancellor, managed to secure powerful allies and strengthen the Emperor's position—his skill in managing the vast secret diplomatic network over the coming years was the main reason why Charles VI once again came to depend upon him. In August 1726 Russia acceded to the Austro-Spanish alliance, and in October Frederick William I of Prussia followed suit by defecting from the Allies with the signing of a mutual defensive treaty with the Emperor.

Despite the conclusion of the brief Anglo-Spanish conflict, manoeuvring between the European powers persisted throughout 1727–28. In 1729 Elisabeth Farnese abandoned the Austro-Spanish alliance. Realizing that Charles VI could not be drawn into the marriage pact she wanted, Elisabeth concluded that the best way to secure her son's succession to Parma and Tuscany now lay with Britain and France. To Eugene it was 'an event that which is seldom to be found in history'. Following the Prince's determined lead to resist all pressure, Charles VI sent troops into Italy to prevent the entry of Spanish garrisons into the contested duchies. By the beginning of 1730 Eugene, who had remained bellicose throughout the whole period, was again in control of Austrian policy.

In Britain there now emerged a new political re-alignment as the Anglo-French entente became increasingly defunct. Believing that a resurgent France now posed the greatest danger to their security British ministers, headed by Robert Walpole, moved to reform the Anglo-Austrian Alliance, leading to the signing of the Second Treaty of Vienna on 16 March 1731. Eugene had been the Austrian minister most responsible for the alliance, believing once again it would provide security against France and Spain. The treaty compelled Charles VI to sacrifice the Ostend Company and accept, unequivocally, the accession of Don Charles to Parma and Tuscany. In return King George II as King of Great Britain and Elector of Electorate of Hanover guaranteed the Pragmatic Sanction, the device to secure the rights of the Emperor's daughter, Maria Theresa, to the entire Habsburg inheritance. It was largely through Eugene's diplomacy that in January 1732 the Imperial diet also guaranteed the Pragmatic Sanction which, together with the Treaties with Britain, Russia, and Prussia, marked the culmination of the Prince's diplomacy. But the Treaty of Vienna had infuriated the court of King Louis XV: the French had been ignored and the Pragmatic Sanction guaranteed, thus increasing Habsburg influence and confirming Austria's vast territorial size. The Emperor also intended Maria Theresa to marry Duke Francis Stephen of Lorraine which would present an unacceptable threat on France's border. By the beginning of 1733 the French army was ready for war: all that was needed was the excuse.
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