Polish troops held Moscow—then lost Russia forever
While Russia reeled through the Time of Troubles, famine, and rival false tsars, the Polish–Lithuanian Commonwealth pushed east. After the 1610 Battle of Klushino, Polish units entered Moscow and boyars even elected a Polish prince tsar. Within two years a popular army drove them out—and a new Romanov dynasty began.
The formal war ran from 1609 to 1618, but Polish historiography often peels off earlier "Dimitriads" (1604–1606 and 1607–1609) as separate bids to seat a friendly tsar. Russia's crisis followed Tsar Feodor I's 1598 death, the Rurik line's end, and a catastrophic famine from 1601 to 1603 linked to global cold after a South American volcanic eruption. Boris Godunov (1598–1605) and later Vasili IV Shuysky (1606–1610) faced pretenders backed by restless boyars and border magnates. In 1600 Chancellor Lew Sapieha offered Moscow a future personal union; Godunov refused and only prolonged the old Jam Zapolski truce to 1622.
King Sigismund III Vasa lacked cash, troops, and popular appetite for a full invasion, yet chaos invited private enterprise. False Dmitry I crossed with roughly 3,500 magnate soldiers and mercenaries in June 1604, won at Novhorod-Siverskyi, then nearly collapsed at Dobrynichi until Godunov's death on 13 April 1605 opened Moscow. Crowning on 21 July and marriage to Catholic Marina Mniszech inflamed Orthodox opinion. After further skirmishing, Russia's Swedish alliance prompted Sigismund's official 1609 declaration of war, aimed at territory and at weakening Sweden. Early Polish victories culminated at Klushino in 1610; Poles entered the capital as Sweden pivoted into the Ingrian War (1610–1617).
In September 1610 the Seven Boyars chose Sigismund's son Władysław as tsar, but the king refused unless Muscovites abandoned Orthodoxy for Catholicism—shattering the pro-Polish coalition. Kuzma Minin and Prince Dmitry Pozharsky raised a new host in 1611; Poles took Smolensk that June yet were expelled from Moscow in September 1612. In March 1613 the Zemsky Sobor elected Michael Romanov, ending the Troubles and founding a dynasty that lasted until 1917. After quiet years, the Truce of Deulino in 1618 handed the commonwealth some lands while leaving Russia independent. The clash seeded lasting Russo-Polish rivalry and a rich cultural afterlife from Pushkin's Boris Godunov to Glinka's A Life for the Tsar.
Source: Polish–Russian War (1609–1618)
