1st Legions Infantry Division ( Poland ) Polish 1st Legions Infantry Division ( " 1 . Dywizja Piechoty Legionów " ) was a tactical unit of the Polish Army between the World Wars . Formed on February 20 , 1919 , partially of veterans of the I Brigade of the Polish Legions , the unit saw extensive action during the Polish - Bolshevik War and World War II . As one of the most experienced and best equipped Polish divisions , it fought in many of the most notable battles of the Polish - Bolshevik War of 1919 and 1920 . Among them was the operation of liberation of Wilno and Battle of Dyneburg in Daugavpils , Latvia ( as part of Rydz - Śmigły ' s 3rd Army and under his personal command , although the actual commanding officer was Michał Karaszewicz - Tokarzewski ) . During the Kiev Offensive of spring of 1920 , the division formed the core of " Rydz - Śmigły Operational Group " and took part in the battles of Zhytomir ( April 25 ) and capturing the city of Kiev itself ( May 7 ) . After the Polish withdrawal , the unit took part in heavy retreat battles and shielded the retreat of the rest of the Polish forces . After several battles against the 1st Cavalry Army , the division broke off and reached the area of the Wieprz River , from where it started the counter - offensive during the Battle of Warsaw . On the second day of the Polish offensive , on August 16 , the division managed to outflank the Bolshevik Mozyr Group by a forced march of over 56 kilometres . After that the division , then commanded by Stefan Dąb - Biernacki , was attached to the 2nd Army and took part in the second biggest battle of the war , the Battle of the Niemen River . During the battle , the unit formed core of the " Wilno Group " and took part in a successful outflanking manoeuvre of the Bolshevik forces centered around the city of Grodno . After that the division was moved to the rear and took part in shielding the border with Lithuania during Lucjan Żeligowski ' s forming of the Central Lithuanian Republic . After the war , the division was partially demobilized and stationed in Wilno as an en cadre divisional core . Before the outbreak of World War II , the division was partially mobilized in March 1939 . As a part of the " Wyszków Operational Group " it was to shield the northern approaches of Warsaw from the German assault from East Prussia . After the outbreak of the Polish Defensive War , the division became fully mobilized and on September 4 , 1939 , it made contact with enemy troops in the forests around Długosiodło . On September 7 it took part in heavy fighting near Pułtusk , but was outnumbered 3 to 1 and ordered to retreat southwards to defend the Bug River river line between Kamieńczyk and Wyszków . Reinforced by 98th Heavy Artillery Detachment and 61st Light Artillery Detachment , the division successfully repelled a German assault near Brańszczyk , after which it began delaying actions while retreating towards Kałuszyn . On September 11 that town was seized by German units and had to be retaken by force during heavy street fighting in the dark . From there , general Wincenty Kowalski planned a counter - assault of his division . In what became known as the Battle of Kałuszyn , on September 13 , the division started an all - out assault on German positions in nearby villages . After heavy fighting the division broke through the third line of German defences in the villages of Lipiny , Debowiec , Wola Wodyńska and Oleśnica . It finally broke through the German lines at Jagodno , but also suffered heavy casualties and lost most of its artillery and logistical support . Dispersed units crossed the German lines and joined several different Polish units , some of them formed ad hoc . The biggest group was rallied by the division commander , but now numbered only three infantry companies out of an original three regiments . These troops broke through the forests near Radzyń Podlaski to reach the units of Gen . Stefan Dąb - Biernacki and on September 22 took part in the successful Battle of Falków against parts of the German 8th Infantry Division . Shortly afterwards the division effectively ceased to exist .