The crucial role, however, was assigned to the approximately 20,000-strong, newly formed Task Force (also translated as "Assault Group" or "Shock Army", from Polish "Grupa Uderzeniowa"), under the personal command of Piłsudski. This unit, composed of the most elite Polish units from the southern front, was to be reinforced by General Leonard Skierski's 4th Army and General Zygmunt Zieliński's 3rd Army. After retreating from the Bug River area, those armies had not moved directly toward Warsaw but had crossed the Wieprz River and broken off contact with their pursuers, thus confusing the enemy as to their whereabouts. The Assault Group's assignment was to spearhead a rapid offensive from their southern position in the Vistula-Wieprz River triangle. They were supposed to advance north, targeting a weak spot that the Polish intelligence thought to have found in between the Soviet Western and Southwestern Fronts, where their communications relied on the weak Mozyr Group. The aim of this operation was to throw the Soviet Western Front into chaos and separate it from its reserves. According to the plan, Sikorski's 5th Army and the advancing Assault Group would meet near the East Prussian border, leaving the Soviets trapped in an encirclement.