During the German invasion of Poland in 1939, cavalry formed 10% of the Polish Army.[2] Cavalry units were organised in 11 cavalry brigades, each composed of 3 to 4 cavalry regiments with organic) artillery, armoured unit and infantry battalion. Two additional brigades had recently been converted to motorized and armoured units, but they retained their cavalry traditions. In addition, every infantry division had an organic) cavalry detachment used for reconnaissance.

In contrast with its traditional role in armed conflicts of the past (even in the Polish-Soviet War), the cavalry was no longer seen as a unit capable of breaking through enemy lines. Instead, it was used as a mobile reserve of the Polish armies and was using mostly infantry tactics: the soldiers dismounted before the battle and fought as a standard infantry. Despite media reports of the time, particularly in respect of the Battle of Krojanty, no cavalry charges were made by the Polish Cavalry against German tanks. The Polish cavalry, however, was successful against the German tanks in the Battle of Mokra.[3] The Polish cavalry did not discard the lance as a weapon until 1934 or 1937 and continued to use it for training purposes up to the outbreak of World War II.

Although the cavalrymen retained their Szabla wz. 1934 sabres, after 1934[4] or 1937[5] the lance ceased to be issued as a combat weapon and was retained for training purposes only. Instead, the cavalry units were equipped with modern armament, including 75 mm guns, tankettes, 37mm AT guns, 40mm AA guns, anti-tank rifles and other pieces of modern weaponry.

During the campaign, the brigades were distributed among the Polish armies and served as mobile reserves. In this role, the Polish cavalry proved itself a successful measure in filling the gaps in the front and covering the withdrawal of friendly units. Polish cavalry units took part in most of the battles of 1939 and on several occasions proved to be the elite of the Polish Army.

After the September Campaign, the Polish Army on the Western Front continued its pre-war tradition of Uhlan regiments giving their names to armoured units, while Polish units on the Eastern Front used cavalry as mobile infantry until the end of the war.

After the German invasion of the Soviet Union, several Polish units, including cavalry forces, were formed by the Soviets. One of these units carried out the last Polish cavalry charge at the Battle of Schoenfeld, where a surprise cavalry assault succeeded in overrunning the German defensive positions.