Harassing fire Harassing fire is a form of psychological warfare in which an enemy force is subjected to random , unpredictable and intermittent small - arms or artillery fire over an extended period of time ( usually at night and times of low conflict intensity ) in an effort to undermine morale , increase the enemy ' s stress levels and deny them the opportunity for sleep , rest and resupply . This lowers the enemy ' s overall readiness and fighting ability , acting as a force multiplier for the harassing force . As the name suggests , harassing fire is undertaken as an extreme form of nuisance without a major effort to produce significant casualties or to support a larger attack . The intent is to merely ensure the enemy can never fully rest or attend to non - combat related tasks and must always be alert and in cover from incoming fire . For this reason , harassing fire is often conducted at night ( or around the clock if resources allow ) and by a small number of guns or artillery pieces rather than the whole contingent . The denial of sleep and constant alert state it induces is physically and psychologically unsustainable by infantry forces for any length of time , and eventually causes severe degenerative stress and degradation of the force ' s combat abilities . For this reason , it has been a standard and efficacious tactic used since the introduction of the projectile weapon . History . Antiquity . Harassing fire became commonplace after the invention of the catapault and trebuchet , which could be used to hurl a variety of harmful objects over fortified wall s during the siege of a city or castle . Since such a siege could drag on for months or years if the attackers were unable to forcibly breach the walls , an alternative plan called for patience coupled with regular harassing fire in an effort to induce the defenders to surrender due to low morale , disease and starvation . Aside from lethal projectiles such as stones and iron balls , the artillery of the time would also throw harassment projectiles : rotting bodies ( both men and animals ) , plague - infected corpses , piles of human excrement , beehives and the severed heads of captured enemy prisoners of war , all in an effort to harass and discourage the besieged defenders until they surrendered . World War I . Harassing fire entered a new phase following the widespread mass - production of cheap , long - range high explosive artillery in World War I , assisted by the static , inflexible nature of the defensive positions faced . Whole batteries on all sides of the conflict were dedicated to harassing fire ( especially prior to a planned infantry attack ) and the concept was refined to a science , complete with formulae for shells - per - hour and pattern density to ensure sleep and resupply were statistically impossible for the targeted force . In most cases , resupply and relief was already nearly impossible during the day due to artillery observer s , and the addition of random harassing fire at night meant even fewer replacements and supplies could reach the front . The shell shock this eventually induced in the enemy was usually a disassociative psychological reaction to months of unending explosions , fear , hunger and sleep deprivation . World War II . Harassing fire continued to be an effective and widespread practice in World War II as bomber aircraft and missiles were added to the equation . Soviet forces famously formed three all - female harassment bomber regiments in 1942 ( the 586th , 587th and 588th ) equipped with obsolescent Polikarpov Po - 2 biplane trainer aircraft . Although very slow , poorly armed and virtually defenseless during the day , the Po - 2 was exceptionally cheap and reliable , could carry two small ( 44 lb . ) HE bombs and was nearly silent when flown by an expert at night ; the small , low - RPM piston engine produced only a muted rattling for a sound signature , far quieter and less identifiable than the turbocharged aero - engines of a modern fighter / bomber . As a result , it was much harder to pinpoint the plane ' s exact bearing or distance and gave the target very little warning of their arrival . Although initially sneered at by the Germans , who called the Po - 2 " Rusfaner " ( " Russian plywood " ) or " Die Nähmaschine " ( " the sewing machine " ) , it proved unexpectedly effective at night harassment attacks on rear areas of the German lines , flying so low and slow the German fighters were unable to locate or engage them . The elderly wood - and - fabric plane also proved both highly resistant to standard armor piercing anti - aircraft ammunition , as well as invisible to modern radar , leaving the Germans with no option but blind saturation flak and searchlights , neither of which were particularly successful and helped further ensure nobody in the camp could get any restful sleep . Soon the Germans frustratedly dubbed the women pilots " Die Nachthexen " , " The Night Witches " , and Luftwaffe pilots and anti - aircraft gunners were promised the Iron Cross if they managed to shoot down even a single Po - 2 . Harassing fire also expanded to civilians as terror bombing of cities became the norm . In a 1944 report on the recent introduction of the V - 1 Flying Bomb , Time Magazine referred to the attacks on London as a form of harassing fire , since they were random and frightening attacks ( usually at night ) designed to damage English civilian morale rather than directly disable members of the British military . A tired , frightened worker would produce less war material at their daily factory jobs , they opined . Modern day . The concept continues to be relevant in modern warfare and remains in the artillery curriculum of the US Army War College and the US Army ' s War Plans Division .