The growing Imperial ambitions of the house of Habsburg had developed into a menace to Poland's international position : they now threatened to outflank and encircle Poland on the southern side. Bathory proposed to counteract them by the project of a union with Russia and a joint crusade against Turkey under the auspices of the Pope. This grandiose plan would have given Poland again a firm footing on the shore of "her second sea"— the Black sea—which she had reached once before in the time of the Jagiellos. But the idea was carried with Bathory to his grave on his sudden death in 1586.
The Vasa period of Polish his tory, which began with the election of Sigismund, son of John III., king of Sweden and of a Jagiello princess, was the epoch of last and lost chances. The collapse of the Muscovite tsardom in the east, and the submersion of the German empire in the west by the Thirty Years' War, presented Poland with an unpre cedented opportunity of consolidating, once for all, her hard-won position as the dominating power between central and eastern Europe : she might even have wrested the best part of the Baltic littoral from the Scandinavian powers, and pushed Russia back beyond the Volga. That this was not achieved, was partly due to the class spirit and blind selfishness of the Polish gentry. Apa thetic towards vital problems of foreign policy, and unwilling to make material sacrifices to the cause of national defence, they persisted in a doctrinaire defence of "republican liberty" at the very time when the need of a strong central executive was more urgent than ever.
But other grave causes of failure were not wanting. One of them consists in the very personality of the new foreign-bred king : the tenacity with which he clung to his hereditary rights to the Swedish crown, involved Poland in unnecessary wars with Sweden at most inopportune times; and his bigoted devotion to the cause of Catholicism introduced a new spirit of religious fanaticism and persecution into the atmosphere of a country hitherto distin guished for toleration, while the same bigotry served Poland's interests very ill abroad. Poland's greatest statesman of the time, Jan Zamoyski, discovered in the earliest years of the reign that the king, who had married a Habsburg princess, was willing to surrender the crown of Poland to an Austrian archduke, and to return to his native Sweden in order to bring it back to the Catholic fold. Zamoyski, who had himself placed Sigismund on the throne by conquering a rival Austrian candidate, was natur ally indignant, and the whole disgraceful affair of the king's secret negotiations with Austria culminated in his having to answer the charges of a special "Court of Inquisition" (1592)—the first time that the prestige of the crown in Poland was exposed to such an ordeal.
It was only where the expansion of Catholicism served the interests of the Polish state that Zamoyski saw eye to eye with the king's Catholic zeal. Thus, he became in strumental in creating, at the synod of BrzegC in 1596, the Uniat Church as a half-way house for those of the republic's Greek Orthodox citizens who were willing to recognize the supremacy of Rome, but desired to preserve their accustomed Eastern ritual and Slavonic liturgy. The Uniat Church served the purpose of drawing a large section of the population of the Eastern border provinces out of the orbit of Russian and into that of Polish in fluences ; but by the antagonisms which soon began between Uniats and Non-Uniats, it became in itself a source of new troubles for Poland. Besides this, the pride of Poland's Roman Catholic prelates, who looked down on the Uniat hierarchy, forced the Uniat Church into the position of a "peasant religion" and con tributed to making it the social nucleus of anti-Polish Ukrainian nationalism which it remains to-day. Even in Sigismund's time, Austria, competing with Poland for influence in the Eastern Bal kans, began to seduce the Ukrainian element (represented in organized form by the military community of the Cossacks) against Poland—a policy which the same Austria was to resume later in changed form and under different conditions when mis tress of Eastern Galicia.
The dispute over Sigismund's rights to the Swedish crown began, from the earliest years of the reign, to drag its weary course of alternate victories and defeats. At first the Estonia and Latvia of to-day were both territory and principal object of the strife ; in the later stages, Gustavus Adolphus transferred the ground nearer to the heart of Poland by espousing the cause of the Calvinist elector of Branden burg, who had come into possession of East Prussia and thus laid the foundation of a large Protestant power on the Baltic. The danger to Danzig and Poland's corn exports roused even the gentry from their apathy; but in spite of some brilliant victories by sea and land, an armistice towards the end of the reign was highly unfavourable to Poland.