In May 1571, the 120,000-strong Crimean and Turkish army (80,000 Tatars, 33,000 irregular Turks and 7,000 janissaries) led by the khan of Crimea Devlet I Giray, and Big and Small Nogai hordes and troops of Circassians, bypassed the Serpukhov defensive fortifications on the Oka River, crossed the Ugra River and rounded the flank of the 6,000-man Russian army. The sentry troops of Russians were crushed by the Crimeans. Not having forces to stop the invasion, the Russian army receded to Moscow. The rural Russian population also fled to the capital.
The Crimean army devastated unprotected towns and villages around Moscow, and then set fire to suburbs of the capital. Due to a strong wind, the fire quickly expanded. The townspeople, chased by a fire and refugees, rushed to northern gate of capital. At the gate and in the narrow streets, there was a crush, people "went in three lines went on heads one of another, and top pressed those who were under them". The army, having mixed up with refugees, lost order, and general prince Belsky died in a fire.
Within three hours, Moscow burnt out completely. In one more day, the Crimean army, sated with its pillage, left on the Ryazan road to the steppes. Contemporaries counted up to 80,000 victims of the invasion in 1571, with 150,000 Russian taken as captives. Papal ambassador Possevin testified of the devastation: he counted in 1580 no more than 30,000 inhabitants of Moscow, although in 1520 the Moscow population was about 100,000.