10th Motorized Cavalry Brigade ( Poland ) The 10th Cavalry Brigade ( ) was a Polish military unit , the only fully operational Polish motorized infantry unit during the Invasion of Poland of 1939 , at the onset of World War II . Commanded by Col . ( later General ) Stanisław Maczek , it is considered the only Polish World War II military unit not to lose a single battle . Organized in 1937 . The unit was organized in February 1937 , partially as an experiment . It was to be a hybrid between a standard motorized infantry brigade and the French concept of " Division legere " . As Polish cavalry generals still had some doubts about the value of mechanized force , there was some opposition against reforming the standard horse - mounted cavalry into motorized units . Testing of the new unit was held in a specially created training ground near Kielce , as well as in the Armoured Units Training School . The brigade was supposed to be a kind of emergency unit in the Commander - in - Chief ’ s reserve . Its task was to screen the areas of concentration of Polish troops , to close gaps made by enemy forces in Polish lines and to fight enemy mechanized units . Action of 1939 . The first exercise in offensive action ( 1939 ) was considered a failure – the brigade proved to be insufficiently equipped in anti - tank ordnance to successfully counter enemy armoured units . It was also considered not versatile enough , especially when compared with a standard cavalry unit , which had much better off - road capabilities and speed . Because of that , several changes in its structure were introduced , which were later copied during the formation of the Warsaw Armoured Cavalry Brigade . The commanding officer of the unit was Col . Stanisław Maczek and the chief of his staff was Maj . Franciszek Skibiński . It is to be noted that , despite being fully motorized , the brigade was still officially named " the 10th Cavalry Brigade " . However , most of the sources refer to it as " Motorized " in order to distinguish the unit from its predecessors . Role during invasion of Poland . After the Invasion of Poland in 1939 , the brigade was attached to the Kraków Army defending Lesser Poland and Silesia . Equipped with only light tanks and tankettes and without one artillery battery , which left the unit with only 8 heavier cannons , it went into battle during the first day of the German invasion of Poland . 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 Beskides . Supported by several battalions of Border Guards and National Defence , the Polish motorized unit fought against two Panzer divisions ( 4th Light Division under von Hubicki and 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 form a mobile reserve during the battle for Lwów and allow other Polish units to withdraw 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 , Marshal of Poland Edward Rydz - Śmigły 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 respect even from the enemy . The Germans called 10th Cavalry Brigade " Die Schwarze Brigade " – " The Black Brigade " , because of the black jackets worn by Polish mechanized troops . In the book " Invincible Black Brigade : Polish 10th Cavalry Brigade 1939 " by Jerzy Majka , the black leather jackets were only worn by officers and NCOs . In addition , the leather jacket was also worn motorcycle troops and armor crewman . Certainly enough black leather to be called " Black Brigade " . Fighting in France . However , it was not the end of its history . With the silent support of Hungarians , most of its soldiers managed to get to France , to join the Polish Army led by General Sikorski . They fought in France in 1940 as the 10th Armoured Cavalry Brigade . After France surrendered , the veterans of " The Black Brigade " went to Great Britain and became the core of the Polish 1st Armoured Division . References . Stanisław Maczek , „ Od podwody do czołga ” , Lublin - London 1990