Against the Polish line the Red Army gathered its Northwest Front led by the young General Mikhail Tukhachevsky. Their numbers exceeded 108,000 infantry and 11,000 cavalry, supported by 722 artillery pieces and 2,913 machine guns. The Soviets at some crucial places outnumbered the Poles four-to-one.Tukhachevsky launched his offensive on 4 July, along the Smolensk-Brest-Litovsk axis, crossing the Auta and Berezina rivers. The northern 3rd Cavalry Corps, led by Gayk Bzhishkyan , were to envelop Polish forces from the north, moving near the Lithuanian and Prussian border . The 4th, 15th, and 3rd Armies were to push west, supported from the south by the 16th Army and Mozyr Group. For three days the outcome of the battle hung in the balance, but Soviet numerical superiority proved decisive and by 7 July Polish forces were in full retreat along the entire front. However, due to the stubborn defense by Polish units, Tukhachevsky's plan to break through the front and push the defenders southwest into the Pinsk Marshes failed.
Question: How many armies were to push west?
Answer: 3