On August 16, the Polish Assault Group commanded by Piłsudski began its march north from the Wieprz River. It faced the Mazyr Group, a Soviet corps that had defeated the Poles during the Kiev operation several months earlier. However, during its pursuit of the retreating Polish armies, the Mozyr Group had lost most of its troops and had been reduced to only one or two divisions covering a 150-kilometre front line on the left flank of the Soviet 16th Army. On the first day of the counteroffensive, only one of the five Polish divisions reported any sort of opposition, while the remaining four, supported by a cavalry brigade, managed to advance north 45 kilometres unopposed. When evening fell, the town of Włodawa had been liberated, and the communication and supply lines of the Soviet 16th Army had been cut. Even Piłsudski was surprised by the extent of these early successes. The Assault Group units covered about 70 kilometres in 36 hours. As planned, it split the Soviet fronts, disrupting the offensive, all without encountering any significant resistance. The Mozyr Group had already been defeated on the first day of the Polish counterattack. Consequently, the Polish armies found what they had hoped for – a large opening between the Soviet fronts. They exploited it ruthlessly, continuing their northward offensive with two armies following and falling on the surprised and confused enemy.On August 18, Tukhachevsky, in his headquarters in Minsk, some 300 miles (500 km) east of Warsaw, realized the extent of his defeat, quickly issuing the orders for the Red Army to retreat and regroup. He wanted to straighten the front line to improve his logistics, regain the initiative and push the Poles back again, but the situation had progressed beyond salvaging. His orders either arrived too late or failed to arrive at all. Soviet General Bzhishkyan's 3rd Cavalry Corps continued to advance toward Pomerania, its lines endangered by the Polish 5th Army, which had finally managed to push back the Red Army and switched over to pursuit. The Polish 1st Legions Infantry Division, in order to cut the enemy's retreat, carried out a forced march, going on the move for up to 21 hours a day, from Lubartów to Białystok – covering 163 miles (262 km) in only six days. Throughout that period, the division engaged the enemy twice. The division's rapid advance allowed it to intercept the 16th Soviet Army, cutting it off from reinforcements near Białystok and forcing most of its troops to surrender.The Soviet armies in the centre of the front fell into chaos. Some divisions continued to fight their way toward Warsaw, while others retreated, lost their cohesion and panicked. Tukhachevsky lost contact with most of his forces, and the Soviet plans were thrown into disorder. Only the 15th Army remained an organized force; it tried to obey Tukhachevsky's orders, shielding the withdrawal of the westernmost extended 4th Army. However, it was defeated twice on August 19 and 20, and joined the general rout of the Red Army's North-Western Front. Tukhachevsky had no choice but to order a full retreat toward the Western Bug River. By August 21, all organized resistance ceased to exist, and by August 31, the Soviet Southwestern Front was completely routed.

Question: what town had been liberated when evening fell?
Answer: Włodawa