Slovak invasion of Poland ( 1939 ) The Slovak invasion of Poland occurred during Nazi Germany ' s invasion of Poland in September 1939 . The recently created Slovak Republic joined the attack , and the Slovak Field Army Bernolák contributed over 50 , 000 soldiers in three divisions . As the main body of the Polish forces were engaged with the German armies farther north of the southern border , the Slovak invasion met only weak resistance and suffered minimal losses . Background . On March 14 , 1939 , the Slovak State was created as a client state of Germany within the area of Slovakia . Prior to this , on November 2 , 1938 , a part of Slovakia containing a substantial Hungarian population ( due to its having been part of Kingdom of Hungary between 1001 and 1920 ) was taken by the Hungarian Army as a result of the First Vienna Award . Small parts of these disputed areas with mixed Polish and Slovak inhabitants belonged to Germany and Poland . The official political pretext for the Slovak participation in the Polish Campaign was a disagreement over a small disputed area on the Poland - Slovakia border . Poland had appropriated this area on December 1 , 1938 , in the aftermath of the Munich Agreement . In addition , some Polish politicians supported Hungary in their effort to include into their state parts inhabited mostly by Hungarians . During secret discussions with the Germans on July 20 – 21 , 1939 , the Slovak government agreed to participate in the aggression against Poland . The Slovaks also agreed to allow Germany to use its territory as the staging area for its troops . On August 26 , the Slovak Republic mobilized its armed forces and created a new field army , codenamed " Bernolák " , that comprised 51 , 306 soldiers . Additionally , 160 , 000 reservists were called , with 115 , 000 entering service until September 20 , 1939 . Order of battle . The Bernolák army group was led by the Slovak Minister of Defense Ferdinand Čatloš , and had its initial headquarters in Spišská Nová Ves , though after September 8 this was moved to Solivar near Prešov . It consisted of : The group was part of the German Army Group South and was subordinated to the 14th Army led by Wilhelm List , contributing to the 14th Army ' s total of five infantry divisions , three mountain divisions , two tank divisions and one air force division . Bernolák ' s task was to prevent a Polish incursion into Slovakia and to support German troops . Their opposition was the Polish Karpaty Army ( Carpathian Army ) , which consisted of infantry units with some light artillery support and no tanks . Campaign . The attack started on September 1 , 1939 at 5 : 00 a . m . The 1st division occupied the village of Javorina and the town of Zakopane , then continued toward Nowy Targ , protecting the German 2nd mountain division from the left . During September 4 – 5 , it engaged in fighting with regular Polish army units . On September 7 the division stopped its advance , 30 km inside Polish territory . Later , the division was pulled back , with one battalion remaining until September 29 to occupy Zakopane , Jurgów and Javorina . The 2nd division was kept in reserve and participated only in mopping - up operations . In this it was supported by the Kalinčiak group . The 3rd division had to protect 170 km of the Slovak border between Stará Ľubovňa and the border with Hungary . It fought minor skirmishes , and after several days moved into Polish territory , ending its advance on September 11 . Two or three Slovak air squadrons ( codenamed " Ľalia " , Lily ) were used for reconnaissance , bombing and close support for German fighters . Two planes were lost ( one to anti - aircraft fire , one to an accidental crash ) , and one enemy plane was shot down . Total Slovak infantry losses during the campaign were 37 dead , 114 wounded and 11 missing . Aftermath . All Slovak units were pulled back until the end of September 1939 . On October 5 , a victorious military parade was held in Poprad . The mobilized units were gradually demobilized and the Army Group Bernolák was disbanded on October 7 . The Slovak Army took around 1 , 350 civilian prisoners in Poland . In February 1940 , around 1 , 200 of these were handed to Germans , and some of the remainder to the Soviet s . The rest were kept in a Slovak prison camp in Lešť . All the disputed territory , whether part of Poland from 1920 or from 1938 , was given to Slovakia ( this was confirmed by a Slovak parliamentary resolution on December 22 , 1939 ) . Adolf Hitler ' s offer to annex Zakopane was rejected . This arrangement lasted until 20 May 1945 , when the border line was returned to its 1920 position . In invading Poland , the Slovak Army tried to regain some prestige lost during humiliating defeat in the Slovak - Hungarian War . In 1941 , Slovakia participated in the Nazi attack on the Soviet Union from its start .