Barrier troops Barrier troops , blocking units , or anti - retreat forces are formations of soldiers normally placed behind regular troops on a battle line to prevent panic or unauthorized withdrawal or retreat . Barrier troops may be utilized simply to raise the morale of front - line troops and for the purpose of constituting a reserve force , or they may be used to prevent unauthorized withdrawal of soldiers from the battlefield by any means , including indiscriminate killing . As troops guarding other units are obviously not available to fight the enemy they are a costly , often desperate , measure . Early history . The concept of barrier troops dates from the earliest days of land warfare , when more experienced troops were regularly placed behind raw recruits to prevent panic and to provide a reserve if needed to stop an enemy advance . Roman legion s were regularly backstopped by experienced " triarii " legionaries of many years ' service . During the Napoleonic Wars , the losses due to troops deserting battle were regularly greater than the losses resulting from combat . Since desertion was relatively easy in that era , the use of barrier troops enabled commanders to retain cohesive fighting units during the course of a long campaign . Barrier troops in the Red Army . In the Red Army of the Soviet Union , the concept of barrier troops first arose in August 1918 with the formation of the ( " zagraditelnye otriady " ) , translated as " blocking troops " or " anti - retreat detachments " ( ) . The barrier troops were composed of personnel drawn from Cheka punitive detachments or from regular Red Army infantry regiments . The first use of the barrier troops by the Red Army occurred in the late summer and fall on the Eastern front during the Russian Civil War , when commander Mikhail Tukhachevsky was authorized by War Commissar Leon Trotsky of the Communist Bolshevik government to station blocking detachments behind unreliable Red Army infantry regiments in the 1st Red Army , with orders to shoot if they either deserted or retreated without permission . In December 1918 Trotsky ordered that additional barrier troops detachments be raised , for attachment to each infantry formation in the Red Army . On December 18 he cabled : " How do things stand with the blocking units ? As far as I am aware they have not been included in our establishment and it appears they have no personnel . It is absolutely essential that we have at least an embryonic network of blocking units and that we work out a procedure for bringing them up to strength and deploying them . " The barrier troops were also used to enforce Bolshevik control over food supplies in areas controlled by the Red Army , a role which soon earned them the hatred of the Russian civilian population . The concept was re - introduced on a large scale during the German – Soviet War . On June 27 , 1941 , in response to reports of unit disintegration in battle and desertion from the ranks in the Soviet Red Army , the 3rd Department ( military counterintelligence of Soviet Army ) of the USSR ' s Narkomat of Defense issued a directive creating mobile barrier forces composed of NKVD personnel to operate on roads , railways , forests , etc . for the purpose of catching ' deserters and suspicious persons ' . These forces were given the acronym " SMERSH " ( from the Russian " Smert shpionam " - Death to spies ) . SMERSH detachments were created from NKVD troops , augmented with counterintelligence operatives , and were under the command of the NKVD . With the continued deterioration of the military situation in the face of the German offensive of 1941 , SMERSH and other NKVD punitive detachments acquired a new mission : to prevent the unauthorized withdrawal of Red Army forces from the battle line . The first troops of this kind were formed in the Bryansk Front on September 5 , 1941 . On September 12 , 1941 Joseph Stalin issued the Stavka Directive No . 1919 ( Директива Ставки ВГК №001919 ) concerning the creation of barrier troops in rifle division s of the Southwestern Front , to suppress panic retreats . Each Red Army division was to have an anti - retreat detachment equipped with transport totalling one company for each regiment . Their primary goal was to maintain strict military discipline and to prevent disintegration of the front line by any means , including the use of machine guns to indiscriminately shoot any personnel retreating without authorization . These barrier troops were usually formed from ordinary military units , and placed under NKVD command . In 1942 , after the creation of penal battalion s by Stavka Directive No . 227 ( Директива Ставки ВГК №227 ) in 1942 , anti - retreat detachments were also used to prevent withdrawal or desertion by penal units as well . However , Penal military unit personnel were always rearguarded by NKVD or SMERSH anti - retreat detachments , and not by regular Red Army infantry forces . As per Order No . 227 each Army should have 3 – 5 barrier squads up to 200 persons each . Usually barrier troops were used as security check points or patrol s who caught deseters in base sections of Fronts , because regular army unit significantly outnumber barrier troops ; therefore , it was not practical to place barrier troops right behind the corps or divisions as it portraits by Western Cold War propaganda . A report to Commissar General of State Security Lavrentiy Beria on October 10 , 1941 noted that since the beginning of the war , NKVD anti - retreat troops had detained a total of 657 , 364 retreating or deserting personnel , of which 25 , 878 were arrested ( of which 10 , 201 were sentenced to death by court martial ) and the rest were returned to active duty . Most of those arrested were later returned to active duty as well . Sometimes barrier troops were involved in battle operations along with regular soldiers , that was noted by Vasilevsky in his directive N 157338 from October 1 , 1942 .