The death of the Emperor Charles VI in October, 1740, was the signal for the outbreak of another European war. All Charles' efforts on behalf of the Pragmatic Sanction proved to have been labour spent in vain. Great Britain, the United Provinces, Spain, Saxony, Poland, Russia, Sardinia, Prussia, most of the smaller German States, and finally France, had agreed to support (1738) the Pragmatic Sanction. The assent of Spain had been bought by the cession of the two Sicilies; of France by that of Lorraine, whose Duke Francis Stephen had married Maria Theresa and was compensated by the Grand Duchy of Tuscany for the loss of his ancestral domain. The only important dissentient was Charles Albert, Elector of Bavaria, who had married the younger daughter of Joseph I and who claimed the succession not only through his wife, but as the nearest male descendant of Ferdinand I. On the death of Charles VI, then, it might have been supposed that Maria Theresa would have succeeded to her inheritance without opposition. This was far from being the case. The Elector of Bavaria put forward his claims and he found unexpected support in Frederick II of Prussia. Frederick had just succeeded his father Frederick William I, and being at once ambitious and without scruples he determined to seize the opportunity for the purpose of territorial aggression. While lulling the suspicions of Vienna by friendly professions, he suddenly, in December, 1740, invaded Silesia. Maria Theresa appealed to the guarantors of the Pragmatic Sanction. She met no active response, but on the part of Spain, Sardinia and France veiled hostility. Great Britain, at war with Spain since 1739, and fearing the intervention of France, confined her efforts to diplomacy; and the only anxiety of the United Provinces was to avoid being drawn into war. An addition was made to the army of 11,000 men and afterwards in 1741, through dread of an attack on the Austrian Netherlands, a further increase of 20,000 was voted. The garrisons and fortifications of the barrier towns were strengthened and some addition was made to the navy. But the policy of the States continued to be vacillating and pusillanimous. The Republican party, who held the reins of power, desiring peace at any price, were above all anxious to be on good terms with France. The Orangist opposition were in favour of joining with England in support of Maria Theresa; but the prince would not take any steps to assert himself, and his partisans, deprived of leadership, could exert little influence. Nor did they obtain much encouragement from England, where Walpole was still intent upon a pacific policy.

The events of 1741, however, were such as to compel a change of attitude. The Prussians were in possession of Silesia; and spoliation, having begun so successfully, became infectious. The aged Fleury was no longer able to restrain the war party in France. In May at Nymphenburg a league was formed by France, Spain, Sardinia, Saxony and Poland, in conjunction with Prussia and Bavaria, to effect the overthrow of Maria Theresa and share her inheritance between them. Resistance seemed hopeless. A Franco-Bavarian army penetrated within a few miles of Vienna, and then overran Bohemia. Charles Albert was crowned King of Bohemia at Prague and then (January, 1742) was elected Emperor under the title of Charles VII.

Before this election took place, however, English mediation had succeeded by the convention of Klein-Schnellendorf in securing a suspension of hostilities (October 9) between Austria and Prussia. This left Frederick in possession of Silesia, but enabled the Queen of Hungary, supported by English and Dutch subsidies, not only to clear Bohemia from its invaders, but to conquer Bavaria. At the very time when Charles Albert was elected Emperor, his own capital was occupied by his enemies. In February, 1742, the long ministry of Walpole came to an end; and the party in favour of a more active participation in the war succeeded to office. George II was now thoroughly alarmed for the safety of his Hanoverian dominions; and Lord Stair was sent to the Hague on a special mission to urge the States to range themselves definitely on the side of Maria Theresa. But fears of a French onslaught on the southern Netherlands still caused timorous counsels to prevail. The French ambassador, De Fenelon, on his part was lavish in vague promises not unmingled with veiled threats, so that the feeble directors of Dutch policy, torn between their duty to treaty obligations urged upon them by England, and their dread of the military power of France, helplessly resolved to cling to neutrality as long as possible. But events proved too strong for them. Without asking their permission, an English force of 16,000 men landed at Ostend and was sent to strengthen the garrison of the barrier fortresses (May, 1742). The warlike operations of this year were on the whole favourable to Maria Theresa, who through English mediation, much against her will, secured peace with Prussia by the cession of Silesia. The treaty between the two powers was signed at Berlin on July 28. Hostilities with France continued; but, though both the Maritime Powers helped Austria with subsidies, neither Great Britain nor the States were at the close of the year officially at war with the French king.