Answer based on context:

On 2 June 1611 Smolensk had finally fallen to the Poles. 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. The explosion created a large breach in the fortress walls. The fortress fell on the same day.:563 The remaining 3,000 Russian soldiers took refuge in the Assumption Cathedral and blew themselves up with stores of gunpowder to avoid death at the hands of the invaders.:563 Although it was a blow to lose Smolensk, the defeat freed up Russian troops to fight the Commonwealth in Moscow, and the Russian commander at Smolensk, Mikhail Borisovich Shein, was considered a hero for holding out as long as he had. He was captured at Smolensk and remained a prisoner of Poland-Lithuania for the next nine years.

How many days after a mine was thrown in the sewer did the fortress fall?
the same day