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 route 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.