Military engineer Polish military engineers at work in Pakistan A military engineer is primarily responsible for the design and construction of offensive , defensive and logistical structures for warfare . Other duties include the layout , placement , maintenance and dismantling of defensive minefields and the clearing of enemy minefields and the construction and destruction of bridges . In some cases an engineer may be required to destroy something that that same engineer designed and constructed . In some countries , the modern military may comprise engineering units in say , weapon design or procurement , or of non-military civil engineering ( e.g. flood control and river navigation works ) which are not covered by this article . In modern times a military engineer that usually operates during battle and under fire is called a combat engineer . For more modern aspects of military engineering and tools of the combat engineering corps , see combat engineering . Defensive Defensive fortifications are designed to prevent intrusion into the inner works by siege infantry . For minor defensive locations these may only consist of simple walls and ditches . The design principle is to slow down the advance of attackers to where they can be destroyed by defenders from sheltered positions . Most large fortifications are not a single structure but rather a concentric series of fortifications of increasing strength . Fortified cities would typically include an inner `` old town '' ' within walls . Should the city be attacked , those residing outside the walls would enter the inner city . Within this would be a redoubt , or citadel , to which defenders could retreat should the walls or gates be breached . The placement of mines to create minefields and their maintenance and disassembly is another defensive task . When the defender must retreat it is often desirable to destroy anything that may be of use to the enemy , but particularly bridges , as their destruction can slow the advance of the attackers . The retreating forces may also leave booby traps for enemy soldiers , even though these often wreak their havoc upon non-combatant civilians . Offensive In ancient times , fortifications were assaulted by siege engines . These could be projectile throwing devices or simple moving towers that could allow attackers protection while positioning them above the top of the fortification 's walls . The undermining of the defender 's walls by tunneling is called sapping . With the military use of gunpowder this explosive could be placed in tunnels to explode directly under the walls . The most spectacular use of this technique in the 19th century was during the United States ' Civil War . The clearing of enemy minefields is another offensive task . Often the defender in retreat will destroy bridges to impede the attacker . These must be quickly replaced by the attacker in order to retain offensive mobility . In World War II a short portable bridge called the Bailey bridge could be quickly placed by a specialized transporter vehicle . Pontoon bridges have long been used as temporary replacements for destroyed river crossings . Image gallery The design , construction , and demolition of the works and devices shown would be the task of a military engineer in the appropriate era . For a larger view of this gallery see Military engineer ( images ) . Great Wall of China and watchtower ( Ming Dynasty ) Castle at Tarascon , France Replica Catapult siege engine Replica Trebuchet siege engine Bourtange fortification Plans for part of a pentagonal fortress Tarascon Castle moat World War I trench works and shrapnel shelter Drawbridge crossing fortification ditches at Fort Ticonderoga Military Pontoon bridge ( 1940 ) Bailey bridge ( World War II ) Installing a Medium Girder Bridge ( modern ) Landmines ( modern ) See also Bailey bridge Civil engineer Fortification 911th Engineer Company ( Technical Rescue ) - http : //en.wikipedia.org/wiki/911th_Engineer_Company Military engineering projects of World War II : Mulberry Harbour Operation Pluto Military technology and equipment Military engineers Pierre Charles L'Enfant Leslie Groves John Rosworm Royal Engineers Sapper Siege engine Vauban Categories : Architecture and engineering occupations | Engineering | Military occupations | Military engineers | Land warfare | Military engineering In other languages : Svenska | Deutsch | Español | Français | עברית | Italiano | Polski | Português | Suomi 