Salients , re - entrants and pockets A salient is a battlefield feature that projects into enemy territory . The salient is surrounded by the enemy on three sides , making the troops occupying the salient vulnerable . The enemy ' s line facing a salient is referred to as a re - entrant ( an angle pointing inwards ) . A deep salient is vulnerable to being " pinched out " across the base , forming a pocket in which the defenders of the salient become isolated . Salient . Salients can be formed in a number of ways . An attacker can produce a salient in the defender ' s line by either intentionally making a pincer movement around the flanks of a strongpoint , which becomes the tip of the salient , or by making a broad , frontal attack which is held up in the centre but advances on the flanks . An attacker would usually produce a salient in his own line by making a broad , frontal attack that is successful only in the centre , which becomes the tip of the salient . In trench warfare , salients are distinctly defined by the opposing lines of trenches , and they were commonly formed by the failure of a broad frontal attack . The static nature of the trenches meant that forming a pocket was difficult , but the vulnerable nature of salients meant that they were often the focus of attrition battles . Pocket . In mobile warfare , such as the German Blitzkrieg , salients were more likely to be made into pockets which became the focus of annihilation battles . A pocket carries connotations that the encircled forces have not allowed themselves to be encircled intentionally , as they may , when defending a fortified position which is usually called a siege . This is a similar distinction to that made between a skirmish and pitched battle . Soviet military doctrine . Soviet military doctrine distinguishes several sizes of encirclement : The significances of these terms are reflected by the conception of what can be expected in combat in encirclement operations . A cauldron is expected to be “ boiling ” with combat activity , the large enemy forces still quite able to offer “ hot ” resistance in the initial stages of encirclement , and so are to be contained , but not engaged directly . A sack in Soviet experience was often created as a result of operational breakthroughs , and was sometimes as unexpected for the Soviet command as for the enemy . This encirclement , sometimes of an entity of unknown size , tended to move for some time after the initial encirclement due to inherently dynamic nature of operational warfare . By contrast a nest was a reference to a tactical , well - defined and contained encirclement of enemy troops that was seen as a fragile construct of enemy troops unsupported by its parent formation ( the use of the word nest , is similar to the more familiar English expression " machine gun nest " ) . Cerco . In Spanish the word " Cerco " ( literally a fence or siege ) is commonly used to refer to an encircling military force . " Cercos " were particularly common in the Chaco War between Bolivia and Paraguay ( 1932 - 1935 ) and encirclement battles were decisive for the outcome of the war . In the Campo Vía pocket 7 , 500 Bolivians were taken prisoner out of an initial combat force of 10 , 000 . Other " cercos " of the war include the battle of Campo Grande and the battle of Cañada Strongest . Kessel . In German the word " Kessel " ( literally a cauldron ) is commonly used to refer to an encircled military force , and a " Kesselschlacht " ( cauldron battle ) refers to a pincer movement . The common tactic which would leave a Kessel is referred to Keil and Kessel ( Keil means " wedge " ) . The term is sometimes borrowed for use in English texts about World War II . Another use of " Kessel " is to refer to " Kessel fever , " the panic and hopelessness felt by any troops who were surrounded with little or no chance of escape . Examples of " Kessel " battles are : Also , during the Battle of Arnhem , the Germans referred to the pocket of trapped British Paratroops as the " Hexenkessel " ( lit . The Witches ' Cauldron ) . Motti . Motti is Finnish military slang for a totally encircled enemy unit . The tactic of encircling it is called motitus , literally meaning the formation of an isolated block or " motti " , but in effect meaning an " entrapment " or " envelopment " . The word " motti " is borrowed from the Swedish " mått " , or " measure " which means one cubic meter of firewood or pulpwood . When collecting timber for these purposes , the logs were cut and stacked in 1 m³ cubical stacks , each one a " motti " , which would be left scattered in the woods to be picked up later . The word also means " mug " in many Finnish dialects ; " motti " is thus related to " kessel " . A " motti " in military tactics therefore means the formation of " bite sized " enemy units which are easier to contain and deal with . This tactic of envelopment was used extensively by the Finnish forces in the Winter War and the Continuation War to good effect . It was especially effective against some of the mechanized units of the Soviet Army , which were effectively restricted to the long and narrow forest roads with virtually no way other than forwards or backwards . Once committed to a road , the Soviet troops effectively were trapped . Unlike the mechanized units of the Soviets , the Finnish troops could move quickly through the forests on skis and break columns of armoured Soviet units into smaller chunks ( e . g . , by felling trees along the road ) . Once the large column was split up into smaller armoured units , the Finnish forces attacking from within the forest could strike the weakened column . The smaller pockets of enemy troops could then be dealt with individually by concentrating forces on all sides against the entrapped unit . A " motitus " is therefore a double envelopment manoeuvre , using the ability of light troops to travel over rough ground to encircle enemy troops on a road . Heavily outnumbered but mobile forces could easily immobilize an enemy many times more numerous . By cutting the enemy columns or units into smaller groups and then encircle them with light and mobile forces , such as ski - troops during winter a smaller force can overwhelm a much larger force . If the encircled enemy unit was too strong , or if attacking it would have entailed an unacceptably high cost , e . g . , because of a lack of heavy equipment , the " motti " was usually left to " stew " until it ran out of food , fuel , supplies , and ammunition and was weakened enough to be eliminated . Some of the larger mottis held out until the end of the war because they were resupplied by air . Being trapped , these units were therefore not available for battle operations . The largest motti battles in the Winter War occurred at the Battle of Suomussalmi . Three Finnish regiments enveloped and destroyed two Soviet divisions as well as a tank brigade trapped on a road . References . Notes