During the
Invasion of Poland in September 1939, the brigade was attached to the
Kraków Army defending
Lesser Poland and
Silesia. Equipped with only light tanks and tankettes and without a battalion ("dywizjon") of heavy artillery attached to it, which left the unit with only 8 heavier cannons, it went into battle during the first day of the German invasion. After the
Battle of Jordanów Maczek's unit faced the entire German XVIII Corps of General
Eugen Beyer and successfully shielded the southern flank of the Polish forces along the
Beskids. Supported by several battalions of
Border Guards and
National Defense forces, the Polish motorized unit fought against two Panzer divisions (
4th Light Division under
von Hubicki and the
2nd Panzer Division under
Veiel), as well as the
3rd Mountain Division under
Eduard Dietl. For five days Maczek's brigade effectively slowed the German advance. Despite numerical and technical superiority, the German units' daily gain was no more than 10 kilometres. Polish soldiers took advantage of difficult, mountainous terrain, stopping German attacks and occasionally counter-attacking. However, after the front of the Kraków Army was broken to the north of brigade's position, it was pulled out from the front line. The brigade then fought as a screening unit, defending the bridges and fords in
Lesser Poland, until it arrived in
Lwów and joined the city's defenders. The unit was to be formed into a mobile reserve during the
battle for Lwów to facilitate the withdrawal of other Polish units towards the
Romanian Bridgehead. However, the plan was made obsolete by the invasion of Poland by the
Soviet Union on September 17. After two days,
Edward Rydz-Śmigły,
Marshal of Poland ordered the brigade to cross the
Hungarian border. Colonel Maczek's brigade was interned in Hungary. The unit lost about half of its men, but was never defeated in open combat, gaining even the enemy's respect. The Germans called the 10th Cavalry Brigade "Die Schwarze Brigade" – "The Black Brigade", because of the black jackets worn by the Polish mechanized troops. In his book
Invincible Black Brigade: Polish 10th Cavalry Brigade 1939, the author Jerzy Majka states that the black leather jackets were worn only by officers and NCOs. They were also worn by motorcycle troops and armour crewman - certainly enough black leather to acquire the nickname "The Black Brigade". ==Fighting in France==