Among the great wars of history there are few, if any, instances of so long and successfully sustained a struggle, against enormous odds, as that of the Seven Years' War, maintained by Prussia--then a small and comparatively insignificant kingdom--against Russia, Austria, and France simultaneously, who were aided also by the forces of most of the minor principalities of Germany. The population of Prussia was not more than five million, while that of the Allies considerably exceeded a hundred million. Prussia could put, with the greatest efforts, but a hundred and fifty thousand men into the field, and as these were exhausted she had but small reserves to draw upon; while the Allies could, with comparatively little difficulty, put five hundred thousand men into the field, and replenish them as there was occasion. That the struggle was successfully carried on for seven years was due chiefly to the military genius of the king; to his indomitable perseverance; and to a resolution that no disaster could shake.
Although it was not, nominally, a war for religion, the consequences were as great and important as those which arose from the Thirty Years' War. Had Prussia been crushed and divided, Protestantism would have disappeared in Germany, and the whole course of subsequent events would have been changed.