Once committed to the Russian alliance, however, he became the faithful henchman of the emperor Alexander, whose fascinating personality exercised over him to the last a singular power, and began that influence of Russia at the court of Berlin which was to last till Frederick William IV.'s supposed Liberalism was to shatter the cordiality of the _entente_. That during and after the settlement of 1815 Frederick William played a very secondary part in European affairs is explicable as well by his character as by the absorbing character of the internal problems of Prussia. He was one of the original co-signatories of the Holy Alliance, though, in common with most, he signed it with reluctance; and in the counsels of the Grand Alliance he allowed himself to be practically subordinated to Alexander and later to Metternich. In a ruler of his character it is not surprising that the Revolution and its developments had produced an unconquerable suspicion of constitutional principles and methods, which the Liberal agitations in Germany tended to increase. At the various congresses, from Aix-la-Chapelle (1818) to Verona (1822), therefore, he showed himself heartily in sympathy with the repressive policy formulated in the Troppau Protocol. The promise of a constitution, which in the excitement of the War of Liberation he had made to his people, remained unfulfilled partly owing to this mental attitude, partly, however, to the all but insuperable difficulties in the way of its execution. But though reluctant to play the part of a constitutional king, Frederick William maintained to the full the traditional character of "first servant of the state." Though he chastised Liberal professors and turbulent students, it was in the spirit of a benevolent _Landesvater_; and he laboured assiduously at the enormous task of administrative reconstruction necessitated by the problem of welding the heterogeneous elements of the new Prussian kingdom into a united whole. He was sincerely religious; but his well-meant efforts to unite the Lutheran and Reformed Churches, in celebration of the tercentenary of the Reformation (1817), revealed the limits of his paternal power; eleven years passed in vain attempts to devise common formulae; a stubborn Lutheran minority had to be coerced by military force, the confiscation of their churches and the imprisonment or exile of their pastors; not till 1834 was outward union secured on the basis of common worship but separate symbols, the opponents of the measure being forbidden to form communities of their own. With the Roman Church, too, the king came into conflict on the vexed question of "mixed marriages," a conflict in which the Vatican gained an easy victory (see BUNSEN, C. C. J., BARON VON).