There is a trope about no one ever conquering Russia. But it is true that Poland-Lithuania did. But, it isn't just as simple as them marching a superior army into Russia and winning (see Mongols). The point where the Polish-Lithuanian Commonwealth invaded and captured Moscow for two years was during a succession crisis in Russia. Russia had a crisis following the death of Ivan IV (Ivan the Terrible) since his heir apparent was killed by... Ivan the Terrible. Following that the other son took over, where there was some question about the mental capacity of the new Tsar. Coupled with poor health and no sons, he died and thus started the Russian Time of Troubles. Feodor was the last of the line of "Rurik" or the original ruler of Rus. This descended the Tsardom into crisis. Poland-Lithuinian used the troubles as a catalyst to expand their power, and propped up false Tsar's. Notably a list of False Dmitri's, the youngest son of Ivan the Terrible. Civil War raged with the crisis, fueled by uncertainty and civil war over the ruler of Russia and of the kingdom itself. Ultimately during this the Poland-Lithunian Commonwealth invaded and held the city for a period of around two years.

Ultimately the Russians fought for own self-rule and then the boyars (Russian nobility) chose their new ruler, Mikhail Romanov which started the Romanov dynasty that lasted until the fall of the Russian Empire and the ascension of the Soviet Union. The start of the Romanov dynasty did not mark the end of the Time of Troubles, but it began to cure and with it along with an uprising in Moscow and some wins over the Polish/Lithuanian army led to a treaty to be signed.