Russia had been experiencing the Time of Troubles since the death of Tsar Feodor I in 1598, which caused political instability and a violent succession crisis upon the extinction of the Rurik dynasty; furthermore, a major famine ravaged the country from 1601 to 1603.

The King of Poland, Sigismund III Vasa, declared war on Russia in response in 1609, aiming to gain territorial concessions and to weaken Sweden's ally.

In late 1600, a Polish diplomatic mission led by Chancellor Lew Sapieha with Eliasz Pielgrzymowski and Stanisław Warszycki arrived in Moscow and proposed an alliance between the Commonwealth and Russia, which would include a future personal union.

However, as the situation in Russia deteriorated, Sigismund and many Commonwealth magnates, especially those with estates and forces near the Russian border, began to look for a way to profit from the chaos and weakness of their eastern neighbour.

Advocates for a union of Poland–Lithuania with Russia proposed a plan similar to the original Polish–Lithuanian Union of Lublin involving a common foreign policy and military; the right for nobility to choose the place where they would live and to buy landed estates; removal of barriers for trade and transit; introduction of a single currency; increased religious tolerance in Russia (especially the right to build churches of non-Orthodox faiths); and the sending of boyar children for education in more developed Polish academies (like the Jagiellonian University).

However, the impostor False Dmitry I appeared in Poland in 1603 and soon found enough support among powerful magnates such as Michał Wiśniowiecki, Lew, and Jan Piotr Sapieha, who provided him with funds for a campaign against Godunov.

In addition, both Polish magnates and Russian boyars advanced plans for a union between the Commonwealth and Russia, similar to the one Lew Sapieha had discussed in 1600 (when the idea had been dismissed by Godunov).

Finally, the proponents of Catholicism saw in Dmitry a tool to spread the influence of their Church eastwards, and after promises of a united Catholic dominated Russo-Polish entity waging a war on the Ottoman Empire, Jesuits also provided him with funds and education.

Dmitriy's forces fought two engagements with reluctant Russian soldiers; his army won the first at Novhorod-Siverskyi, soon capturing Chernigov, Putivl, Sevsk, and Kursk, but badly lost the second Battle of Dobrynichi and nearly disintegrated.

Russian troops began to defect to his side, and, on 1 June, boyars in Moscow imprisoned the newly crowned tsar, Boris's son Feodor II, and the boy's mother, later brutally murdering them.

Thus the boyars, headed by Prince Vasily Shuyski, began to plot against Dmitry and his pro-Polish faction, accusing him of homosexuality, spreading Roman Catholicism and Polish customs, and selling Russia to Jesuits and the Pope.

In 1608 together with Aleksander Kleczkowski, Lisowczycy, leading a few hundred Don Cossacks working for the Commonwealth, ragtag szlachta and mercenaries, defeated the army of tsar Vasili Shuyski led by Zakhary Lyapunov and Ivan Khovansky at the Battle of Zaraysk and captured Mikhailov and Kolomna.

[12]: 563  The Commonwealth king Sigismund III, whose primary goal was to regain the Swedish throne, got permission from the Polish Sejm (Parliament) to declare war on Russia.

He viewed it as an excellent opportunity to expand the Commonwealth's territory and sphere of influence, with hopes that the eventual outcome of the war would Catholicize Orthodox Russia (in this he was strongly supported by the Pope) and enable him to defeat Sweden.

This plan also allowed him to give a purpose to the numerous restless former supporters of Zebrzydowski, luring them with promises of wealth and fame awaiting members of the campaign beyond the Commonwealth's eastern border.

A book published that year by the well-travelled Polish Silesian nobleman, courtier and political activist Paweł Palczowski of Palczowic,[14] Kolęda moskiewska (The Muscovite Carol),[14][15] compared Russia to the Indian empires of the New World, full of golden cities and easy to conquer.

Previously, Sigismund had been unwilling to commit the majority of Polish forces or his time to the internal conflict in Russia, but in 1609 those factors made him re-evaluate and drastically change his policy.

A Commonwealth army under the command of Hetman Stanisław Żółkiewski, who was generally opposed to this conflict but could not disobey the king's orders, crossed the border and on 29 September 1609 laid siege to Smolensk, an important city Russia had captured from Lithuania in 1514.

The Poles found it impenetrable; they settled into a long siege, firing artillery into the city, attempting to tunnel under the moat, and building earthen ramparts, remnants of which can still be seen today.

An early attack, led by Hetman Jan Karol Chodkiewicz with 2,000 men, ended in defeat when the unpaid Commonwealth army mutinied and compelled their leader to retreat through the heart of Russia and back to Smolensk.

However, as he feared and predicted, as the Polish–Lithuanian forces pressed eastwards, ravaging Russian lands, and as Sigismund's lack of willingness to compromise became more and more apparent, many supporters of the Poles and of the second False Dmitry left the pro-Polish camp and turned to Shuyski's anti-Polish faction.

Russian forces under Grigory Voluyev[17] were coming to relieve Smolensk and fortified the fort at Tsaryovo-Zaymishche (Carowo, Cariewo, Tsarovo–Zajmiszcze) to bar the Poles' advance on Moscow.

Żółkiewski found himself in an awkward position – he had promised the boyars Prince Władysław to keep the Russian throne for Poland, and he knew that they would not accept Sigismund III, who was unpopular throughout Russia.

Sigismund and Władysław left the city for safer ground as tensions grew, and the small Polish garrison at the Kremlin soon became isolated and subject to increased hostility, as more and more of the formerly pro-Polish boyars began to change factions.

The respected town butcher (literally, a meat-trader) Kuzma Minin oversaw the handling of funds donated by the merchants to form the Second Volunteer Army (Russian: Второе народное ополчение).

After enduring 20 months of siege, two harsh winters and dwindling food supplies, the Russians in Smolensk finally reached their limit as the Polish–Lithuanian troops broke through the city gates.

The Polish army, advised by the runaway traitor Andrei Dedishin, discovered a weakness in the fortress defenses, and on 13 June 1611 Cavalier of Malta Bartłomiej Nowodworski inserted a mine into a sewer canal.

Sigismund, criticized by the Sejm (the Polish parliament made up of the szlachta, who were always reluctant to levy taxes upon themselves to pay for any military force)[12]: 565  for his failure to keep Moscow, received little funding for the army.

In Poland the Dmitriads campaign is remembered as the height of the Polish Golden Age, the time Poles captured Moscow, something that even four million troops from Adolf Hitler's Nazi Germany and other Axis Powers could not manage.

[19][20] In modern Poland, from 2023, every 8 October, The Museum of the Eastern Lands of the Former Commonwealth in Lublin organizes the remembrance celebration about the allowing the Polish troops to take the Kremlin.