In April 1920, Pilsudski invaded all of Ukraine and entered kyiv, earning the enmity of the Soviets forever. By doing so, he hoped to establish a Republic of Ukraine allied with Poland against Russia. His hopes were dashed; all anti-Bolshevist forces having been eliminated
except those based in Crimea
, the dangerously stretched Polish armies stood alone against the victorious Red Army.
At the end of May 1920, the elite (and most famous) of all Russian revolutionary forces - the 1st Cavalry Red Army, the Konarmiya, crossed the border into Ukraine after traveling some 1,170 km in 30 days.
An American pilot from the Polish Air Force gives his impressions:“I never imagined that there could be so many riders in the world! .
This formidable troop of 16,000 cavalry was accompanied by 48 guns, 5 armored artillery trains and 8 armored vehicles; it had been organized by the ambitious Joseph Vissarionovitch Stalin, and was commanded by Semyon Mikhailovitch Boudianny, a fierce, colorful soldier, incomparable leader of men, of exceptional physical strength. With the support of the 12th and 14th Soviet infantry armies, the Konarmiya attacked on May 26. On June 5, the Soviets broke through the Polish rear which, in panic, broke up. In Berdichev, they set fire to a hospital sheltering 600 wounded Poles and Red Cross nurses; the hospital burned down. The Konarmiya thus justified its reputation, and by mid-July all Polish troops had evacuated Ukraine.
To the north the Red armies were commanded by Mikhail Nikolaevich Tukhachevsky, a young man of 27, Stalin's "civil war demon". At the beginning of July 1920, Tukhachevsky's 5 armies numbered about 160,000 men (50,000 more than the Poles) and had a large artillery at their disposal, amassing 595 guns, a three-to-one superiority. Tukhachevsky also had a powerful strike force made up of the 3rd Cavalry Corps (the Kavkor), the 10th and 15th Cavalry Divisions as well as the 164th Rifle Brigade led by Ghia Dmitryievitch Ghai, a former Armenian commander of the Iron Division, nicknamed by the Poles "Gay-Khan".
Maneuvering on the Russian right wing and constantly bypassing the Polish flanks, from July 4 he pushed them back regularly in the direction of Warsaw. On the 14th, Vilna fell, then, on the 22nd,
Grodno where 5,000 Poles were taken prisoner.
After this first confrontation with the Red Army, only two of the 30 Polish tanks engaged in the defense crossed the last bridge over the burning Niemen. The lightning pace of the advance stunned observers. The First World War had not ended for 20 months since a modern military concept had emerged.
Previously, it would have taken months of preparation, tons of high-explosive material and colossal losses for gains of a few hundred meters. This was cavalry-initiated blitzkrieg warfare - a weapon that had proven virtually ineffective on the Western Front.
Observers in Britain and France were unsure what to make of this phenomenon. These powers had dispatched an inter-allied mission which arrived in Poland on July 25 to calm the apprehensions of the Poles who wondered about the help they could receive as a last resort.
In this diplomatic-military mission, the representatives of the government were the former ambassador Jules Jusserand (for France) and the viscount of Abernon (for England); those of the army, General Maxime Weygand, famous Chief of Staff of Marshal Ferdinand Foch, Generalissimo of the Allied Forces in 1918, and British Major-General Sir Perey B. Radcliffe - a former cavalryman, a man of great wisdom.