State Defense Guard ( Czechoslovakia ) State Defense Guard ( in Czech Stráž obrany státu , SOS ) was a military service established in 1936 to protect borders of Czechoslovakia . From 1918 to 1936 border of Czechoslovakia was protected by " " finance guard " " ( " finanční stráž " ) , an armed branch of the Ministry of Finance . Their main task was to carry on customs duty , border protection was secondary . For over decade army and police leadership had suggested to set up an organisation of higher military value . Amid international tensions the new service was established in 1936 . Task of the defense guard was : Members of the guard were local policemen ( " četníci " ) , existing finance guards and members of state police . Later citizens loyal to Czechoslovakia were incorporated ( for example many members of sports organisation Sokol or active anti - fascist Germans ) . Plans were created to support the guard with regular army units to handle local conflicts . Planned size of the service were 38 battalions , but only 31 had been mustered ( one of these inland , in Prague ) . Their equipment were pistols , rifles , light machine guns and grenades . There was not enough of time to equip the units with heavy machine guns . In case of attack the guard was to stop the enemy until main body of the army gets ready for response - more less suicidal mission . Manpower of the guard in September 1938 were 29 , 611 men ( 4 , 917 local policemen , 1 , 674 members of state police , 6 , 438 finance guards , 14 , 755 army reservists , 1 , 827 army members ) . As the tensions between Czechoslovakia , local Germans and Nazi Germany grew up the guard was deployed on the border during May 1938 and stayed there until end of September , when Sudetenland was ceded to Germany . During September the guard fought low level warfare with local German partisans ( " Sudetendeutsches Freikorps " ) and commandos from Germany . After the loss of borderland SOS moved inland on new positions . The clashes had still occurred but on smaller level . As a result of First Vienna Award Czechoslovakia was forced to give up territory to Poland and Hungary ( southern Slovakia and Carpathian Ruthenia ) . While conflicts with Polish forces were minor , clash with Hungarian forces and partisans ( " Szabadczapatok " ) was more intense ( starting in November 1938 ) . From January to March 1939 ( until Czechoslovakia was dissolved ) heavy clashes occurred between Hungarian forces and guard and the army in Ruthenia . Czechoslovakian units were forced to withdraw in three directions - to Slovakia , Poland and Romania . During March the units also faced local insurgents ( " Sičovci " ) attempting to establish independent Ruthenian state . Estimated warfare losses ( both guard and the army ) from May 1938 to April 1939 are 171 dead , 404 injured , over thousand of soldiers taken prisoner and abducted to Germany proper . Losses in Ruthenia are estimated to 40 dead , 120 injured , 17 missing . On December 21 , 1939 government of Protectorate of Bohemia and Moravia disbanded remaining parts of the guard . In Slovak State the guard was disbanded a little later . After the war the organisation was not restored . After communist takeover of power in 1948 special branch of the army called " Border Guard " ( " Pohraniční služba " ) was tasked with border protection .