After the death of the Polish king of the Jagiellonian dynasty, Zygmunt II August, there came a period of so-called "elected kings", preceded by the adoption of the so-called Warsaw Confederation in 1573 on the initiative of Polish heretics, which guaranteed religious tolerance in Poland and thus opened the possibility of electing non-Catholic candidates to the Polish throne.
Among the candidates to the throne during the election (following the confederation) were the son of the Holy Roman Emperor Ernest Habsburg (Catholic), the Moscow tsar Ivan IV the Terrible (Orthodox), the Swedish king John III Vasa (Protestant) and the French prince Henry Valey (Catholic). However, the Polish nobility did not accept the choice of a non-Catholic king and so the first elected king of Poland became a French prince of Catholic faith, who reigned in Poland as King Henry the Valois.
This reign was neither successful nor long, for Henry the Valey did not appear in Poland until January 1574, crowned in February 1574, but already in June 1574 he fled Poland for France when he learned of the death of the French king Charles IX (his brother) and the open chance for the French throne. Perhaps the prospect of the 23-year-old king's planned marriage to 53-year-old Anne, sister of Sigismund II Augustus, planned by Polish magnates, was not much of an incentive to stay in Poland, and the French throne was all the more attractive to Henry.
And since Henry, when made king of France, did not want to return to Poland (nor to his fiancée Anne), the next elected king had to be chosen. In 1575 there were even more candidates, because besides the previous Ernest Habsburg, Ivan the Terrible, John II Vasa, there were also Emperor Maximilian II Habsburg himself, Prince Stefan Batory of Transylvania and many others. The Emperor was a favorite of the Polish Primate, but the nobility looked unfavorably on foreign candidates (after all, no wonder after Henry's escape) and chose as king of Poland... Anna Jagiellonka, sister of Sigismund II Augustus.
Ha, a woman on the throne and a single one at that! Even in today's modern times it is required that the president has a wife and the queen a husband, not to mention those times. The Queen must have a husband! As a result of various deliberations and votes Stefan Batory was chosen as a husband for Anna Jagiellonka. The wedding and coronation took place on May 1, 1576.
And so Stefan Batory became king of Poland and Anna Jagiellon became queen of Poland. The age difference between Anna and Stefan (10 years) was not as big as between Anna and Henry (30 years) but in those days 53 years old woman for 43 years old man might not be so big attraction in bed. Stefan supposedly allowed Anna to come to bed with him, but he was not keen on Anna's bed himself. Whether this was the main reason why he went to war with Russia is hard to say. Batory spent most of his reign as king of Poland on military expeditions. He died in 1586 from illness, according to some, or from poisoning, according to others.
The widowed Anne, however, did not want to continue to reign alone, and gave up the throne to her nephew Sigismund, who, although he came from a Protestant Swedish Vasa family, was himself a Catholic. Sigismund III Vasa married 7 years younger Anna Habsburg, with whom he had a son, Ladislaus. Sigismund III Vasa, son of King John III Vasa of Sweden (and his wife Catherine Jagiellon, sister of Anne Jagiellon) after the death of his father in 1592. crowned also as king of Sweden (thus creating a personal Polish-Swedish union), in religious matters a devout Catholic and associated with the Jesuits (in contact with Andrew Bobola and Piotr Skarga), interested in art and himself practicing artistic crafts, in political matters oriented on political expansion and strengthening the position of Poland, was not averse to alliances, including religious ones. The eastern territories of the Polish-Lithuanian Commonwealth were inhabited by many Orthodox Christians, which had an impact on the political orientation of this people. This was due to the fact that the Orthodox under the leadership of the Moscow Patriarchate, who were completely subordinated to the political goals of the tsar, despite the fact that they lived in the territory of the Commonwealth, could at any time initiate riots leading to the disintegration of the area. In 1596 the so-called Union of Brest was concluded in order to unify the Orthodox and Catholic religions, make the Orthodox and Catholic nobility equal in rights, and also to recognise Rome as the superior of both religions, which were Christian.
Although not to the liking of the Russian tsars, it was a solution for the south-eastern territories of the Polish-Lithuanian Commonwealth. The solution for the north-eastern territories was the Polish-Swedish personal union, as a result of which Sigismund III as king of Poland gained power over Livonia, i.e. the present territories of Lithuania, Latvia and Estonia and further north Swedish territories.
The south-western borders of Poland (beyond which the Habsburgs ruled) were to some extent secured by marriage with the Habsburgs, but the eastern border with the Muscovite state remained open. The problem was additionally complicated by wars which Moscow was fighting over Inflants, either with Poland or Sweden.
The situation worsened in 1599 when the Swedish Protestant party dethroned Sigismund in Sweden (Sigismund never acknowledged this act), because from that time on the Commonwealth had two opponents: Russia and Sweden, which simply meant wars.
And from 1600 the Swedes' push southward begins. One by one Swedes captured Polish strongholds in Livonia. Although the battle of Kircholm and the total victory of Chodkiewicz stopped this invasion, the Polish-Swedish wars continued for many years. Sweden had a natural ally in the wars with the Republic of Poland: Russia.
In 1609 king Charles Suderman of Sweden and tsar Vasily IV of Russia made a treaty in Viipuri that in exchange for ceding Polish strongholds in Livonia, Russia would enter the war with Poland.
It was in Sweden's interest to recapture Inflants, and probably some desire to retaliate against Sigismund III for his attempts to introduce Catholicism in addition to Protestantism, which was one of the main reasons why Swedish Protestants dethroned Sigismund. The Protestant party was far from the religious tolerance that had been introduced in Poland and believed that Catholicism should be ruthlessly destroyed, at most it could exist as a quiet, private religious circle, never on the decision-making level. Sigismund III was therefore still dangerous for Protestants, after all he was the natural successor to the King of Sweden and a Catholic, if he regained the throne, who knows...
On the other hand, it was in Vasily IV's interest to defend his throne against the so-called Dmitry Samozwansky, the supposed legitimate successors of Ivan the Terrible, who were supported by some Russians and also some Polish magnates. Although officially Sigismund III did not support these activities, unofficially he allowed or turned a blind eye when magnates from the eastern territories of the Polish-Lithuanian Commonwealth conducted such activities. Vasily IV Shuisky himself must have had a lot to answer for, since he first supported the young tsar Fyodor II Godunov (son of tsar Boris Godunov), then he acted as an ally of Dmitri Samozwaniec against Fyodor II Godunov (and after a month and a half of reign as tsar Fyodor II he was killed by Dmitri Samozwaniec's supporters), and then turned against Dmitri, who was killed in Moscow - after an 11-month reign as Tsar of Russia - by troops led by Shuisky. Thus, when Dmitri Samozwaniec No. 2 appeared - claiming to be the tsar miraculously saved from the Moscow massacre - Shuisky must have felt the "breath of death" on his neck. All the more so because there were factions in Russia that were eager to get rid of Vasily IV. In 1609 the Polish troops supporting Dmitri No. 2 were already on the outskirts of Moscow and Dmitri No. 2 himself with his supporters controlled a considerable part of Russia.
When in April 1609 an army of Swedish soldiers, also mercenaries from France, Scotland, Germany and England, gathered in Novgorod the Great, it was clear that there would be an all-out war. In August this year Sigismund III decided to march on Smolensk and a month later besieged the fortress. In February the anti-Tsarist party proposes to Sigismund III that Prince Ladislaus should take over the Moscow throne, but Sigismund III refuses to accept the proposal.
The siege is formally led by Stanislav Żółkiewski, but other magnates want to be equally important, which paralyzes Żółkiewski. When the news comes that Wasyl IV sends an army under his brother's command in the direction of Smolensk, Żółkiewski at the head of only a few thousand soldiers rushes (or maybe he breaks out from Smolensk) to meet a Russian-Swedish army of thirty thousand.
It takes place at Klushino on July 10, 1610. The Poles' victory is total, the Russian-Swedish army ceases to exist, its commanders escape, the road to Moscow is open, the more so as the Russians favour the accession of Prince Ladislaus to the throne.
Having heard about the defeat at Kluszyn, boyars in Moscow arrest Wasyl IV and imprison him in a monastery. Żółkiewski reaches Moscow on 5 August and holds negotiations with the boyars which result in a treaty on 27 August under which prince Władysław becomes the tsar of Russia on condition that he converts to Orthodoxy, abandons the siege of Smoleńsk and returns to Russia the Russian fortresses captured by Poles. On the strength of this treaty - made by Żółkiewski with the Russian boyars - Prince Ladislaus was appointed to the throne of the Tsar of Russia, and the next day the citizens of Moscow took an oath of allegiance to Ladislaus. After all, Wladyslaw Vasa is not some self-deluded person, not a silent murderer of tsars, not a tsar's advisor, not one of the local boyars, but a prince of blood, a prince, a son of the mighty king, who is recognized by the whole world.
Even the Swedish Protestants, who did not want Sigismund for a king, were ready to give the throne to Ladislaus. Wladyslaw as tsar of Russia, king of Sweden and after his father king of Poland could create by personal union the most powerful super empire on earth.
And certainly not everyone liked it.
On September 12 the walls of Moscow are opened to the Polish army, on October 8 Żółkiewski is in Kremlin and takes as prisoners both Shuisky Dmitri - unsuccessful commander from Kluszyn and former tsar Wasyl IV. These prisoners will then be delivered to Warsaw, where they will pay homage to Zygmunt III in the Royal Castle.
Polish army in Moscow - in the Kremlin and in addition with the consent of the locals, the crown of the Tsar of Russia given on a platter! Even religious considerations did not have to stand in the way as there was the Union of Brest, supported by the Pope!
However, Vladislav did not take the throne of Moscow!
Why not!
It is simple. Daddy didn't allow
If not, then no. The Polish army still resides in Moscow for some time, but without the support of the locals, the fate of the Polish troops on foreign soil was obvious: defeat. And so on November 7, 1612 the last Polish troops were thrown out of Kremlin. Because if they don't, they don't. This is now celebrated in Russia as a national holiday.
(Translated with www.DeepL.com/Translator)