From The Making of Eastern Europe: From Prehistory to Postcommunism, by Philip Longworth (Lume Books, 2020), Kindle pp. 225-227:
Like the Hohenzollerns of Prussia, the Habsburgs had a variety of rights and powers in many different lands. They were Archdukes of Austria, hereditary Kings of Bohemia, traditional candidates to the elective throne of Hungary (though the Turks occupied much of it and Transylvania was an autonomous principality); and, besides holding a plethora of other titles, were Emperors of the Holy Roman Empire (again as hereditary candidates), a position which gave them little direct power, but a great deal of prestige and not a little patronage. The Habsburgs, then, governed in various ways at once – sometimes exerting direct authority backed up by force; more often abiding by precedents, negotiating, persuading, exerting influence through their powers to grant titles and make appointments.
Theirs was a ramshackle empire, which had expended much of its wealth and sustained much damage during the Thirty Years’ War; and it was still threatened by powerful enemies, notably Ottoman Turkey and France. Furthermore, although the Habsburgs had been the chief protagonist of the Catholic cause in the war, and although the peace sanctioned their imposing it on all their subjects, it was not practicable to do so in Hungary, where there were many Protestants; and the suppression of Protestantism elsewhere, as in Bohemia, tended to promote sullen resentment which might be exploited in the cause of rebellion. How, then, were these obstacles to Habsburg authority to be overcome? What glue could be found to bind these disparate peoples and territories into a cohesive body politic?
According to a leading authority the recipe called for the mutual support of the dynasty, the Counter-Reformation Church and a cosmopolitanized aristocracy, who formed a community of interest; and the use of religious mysteries, the mystique of kingship and the magic of the arts to hold people in thrall. But the military was also important.
The Habsburgs emerged from the war with a permanent standing army and thereafter strove to enlarge it, though as late as 1683 the establishment was only 36,000. Since this was a professional, disciplined, force which did not normally live off the land, it did not arouse the resentment of the population in the localities where it was stationed, as had formerly been the case. Indeed, in time, the army came to promote loyalty to the dynasty not only among those who served in it (the new permanent armies presented welcome new career opportunities to gentlemen and commoners alike), but among a wider public. The sight of neat ranks of men in attractive uniforms marching by to the invigorating sound of flutes and drums tended to arouse popular enthusiasm, and when the army won victories the dynasty gained prestige.
Nonetheless, as in Russia, the practice of religion and the institution of the Church were recognized as being of prime importance in legitimating the dynasty and promoting deference among its subjects. Both Ferdinand III and his successor Leopold I (1657–1705) were personally devout and, like Alexis of Russia, made public show of it. Leopold often made pilgrimages, visited monasteries three or four times a week and dispensed a great deal of charity to the needy. He also believed oaths, including those he himself swore, to be binding. Yet, like Alexis, insofar as he showed himself to be as pious as any prelate, he felt entitled to interfere in church affairs. Not only did he control the more important ecclesiastical appointments, order special prayers to be said and proclaim religious holidays by decree, he imposed taxes on the clergy and milked the church of funds, plate and valuables as the need arose. One can therefore understand the wry comment of the papal nuncio who wished the Emperor were not quite so pious.