Battle of Piotrków Trybunalski
The Battle of Piotrków Trybunalski was a battle in the Invasion of Poland from the 5 to 6 September 1939, which involved Polish and German tank formations.

Opposing forces

Polish Army 
The core of the Polish force consisted of most of "Prusy" Army's Northern Group. The army, created as the main operational reserve of Polish commander in chief Marshall Edward Rydz-Śmigły was also the last to be mobilised in the summer of 1939. Intended as a reserve of Łódź Army and Kraków Army, the Prusy Army was to support its neighbours and relieve them once the main German attacks are slowed down. However, the Battle of the Border did not gain the Poles enough time to fully mobilise the reserves.

While most of Polish Army had been successfully mobilised prior to 1 September 1939, on that date many sub-units of Prusy Army were still being formed or transported. By 4 September 1939, when the German forces broke through the overstretched Polish defences, the Prusy army was far from battle-ready. Its Northern Group at that date consisted of 29th Infantry Division and Wileńska Cavalry Brigade, with 19th Infantry Division still being formed in the forests to the north-east of Piotrków Trybunalski while the 13th Infantry Division was still waiting for some of its sub-units near the railway hub of Koluszki and did not become available until 6 September. The army was strengthened by a mobile reserve formed by the 1st Light Tank Battalion (armed with modern 7TP tanks) stationed between Opoczno and Końskie, and the 81st Motorised Sappers Battalion.

Apart from units of the Prusy Army, the Polish side also included a number of smaller units from Łódź Army. In the city of Piotrków Trybunalski itself the 146th Infantry Regiment was being mobilised for the 44th Reserve Infantry Division and was dispatched to the front as part of an improvised battle group under Col. Ludwik Czyżewski. In addition, elements of the Wołyńska Cavalry Brigade and the 2nd Legions' Infantry Regiment of the 2nd Legions Infantry Division also took part in the battle as part of Col. Czyżewski's group.

Wehrmacht 
The German force fighting in the battle consisted of the entire XVI Panzer Corps. The unit, part of German 10th Army, was the strongest Panzer corps in the Wehrmacht and on 1 September 1939 included between 616 and 650 tanks of all types (the entire Polish Army had 313 proper tanks altogether, not including reconnaissance tankettes). The XVI Corps included the 1st and 4th Panzer Divisions as well as the 14th and 31st Infantry Divisions.

Battle
As the Germans advanced through Silesia, the 4th and 1st Panzer Divisions headed towards Piotrkow.   The Polish 19th Infantry Division tried to counter-attack on 5 September, but there were many gaps in their lines.  However, the Polish 2nd Tank Battalion entered the defense of the city and their 7TP tanks were successful in destroying 17 Panzers, 2 self-propelled guns and 14 armoured cars, with the loss of only 2 tanks.  However, there were too few Polish tanks and could not prevent the Germans from breaking through the gap between Army Lodz and Army Kraków, even with help from Army Prusy.  That evening, Marshal Rydz-Smigly ordered the Polish forces to withdraw to the east bank of the Vistula.