A combat engineer (also called pioneer or sapper ) is a type of soldier who performs military engineering tasks in support of land forces combat operations. Combat engineers perform a variety of military engineering, tunnel and mine warfare tasks as well as construction and demolition duties in and out of combat zones.  
Combat engineers facilitate the mobility of friendly forces while impeding that of the enemy. They also work to assure the survivability of friendly forces, building fighting positions, fortifications, and roads. They conduct demolition missions and clear minefields manually or through use of specialized vehicles. Common combat engineer missions include construction and breaching of trenches, tank traps and other obstacles and fortifications; obstacle emplacement and bunker construction; route clearance and reconnaissance; bridge and road construction or destruction; emplacement and clearance of land mines; and combined arms breaching. Typically, combat engineers are also trained in infantry tactics and, when required, serve as provisional infantry.      
Combat engineers play a key role in all armed forces of the world. They are invariably found closely integrated into the force structure of divisions, combat brigades, and smaller fighting units.
In many countries, combat engineers provide combat support members of a broader military engineering corps or branch. Other nations have distinct combat engineering corps or branches; they are separate from other types of military engineers. The Danish military engineers' corps, for example, is almost entirely organized into one regiment of combat engineers, simply named Ingeniørregimentet ("The Engineering Regiment").
Combat engineer battalions are usually a part of a brigade combat team. During the War in Afghanistan and the 2003–2011 Iraq War, the U.S. Army tasked its combat engineers with route clearance missions designed to counter rising threats of improvised explosive devices (IEDs). To increase the effectiveness of these units, EOD and mechanic teams were typically embedded with the combat engineer platoon. Due to rising IED threats, the U.S. Army sends some combat engineers to complete Explosive Ordnance Clearance Agent training. 
Individual combat engineers are often assigned as a component of both covert and overt direct action special operations teams. For example, the active duty US Army Special Forces  and its two reserve components, the 19th SFG and 20th SFG of the US Army National Guard,  employ combat engineer sergeants designated by MOS 18C. A Green Berets Operational Detachment Alpha, more commonly known as an "A-Team",  typically consists of 12 men, two of whom are combat engineer sergeants. 
A general combat engineer is often called a pioneer or sapper , terms derived respectively from the French and British armies. In some armies, pioneer and sapper indicate specific military ranks and levels of combat engineers, who work under fire in all seasons and may be allocated to different corps, as they were in the former Soviet Army, or they may be organized in the same corps. Geomatics (surveying and cartography) is another area of military engineering but is often performed by the combat engineers of some nations and in other cases is a separate responsibility, as was formerly the case in the Australian Army. While the officers of a combat engineer unit may be professionally certified civil or mechanical engineers, the non-commissioned members are generally not.[ citation needed ]
In the British, Indian, Canadian, Australian, and New Zealand armies, a sapper is a soldier who has specialized combat engineer training. The term "sapper" in the U.S. Army refers to a person who either possesses the combat engineer military occupational specialty or who has graduated from the Sapper Leader Course, more commonly called "Sapper School." In Sapper School, volunteers from the ranks of combat engineers and other military occupational specialties (most of whom serve in the combat arms) undergo training in combat engineer and infantry battle drills, expedient demolitions, threat weapons, unarmed combat, mountaineering, and water operations. Some of the training in this 28-day course, arguably one of the most challenging in the U.S. Army, features covert infiltration techniques or survival skills. 
In the Israeli Defense Forces, sapper (פלס) is a military profession code denoting a combat engineer who has graduated from various levels of combat engineering training. Sapper 05 is the basic level, Sapper 06 is the general level, Sapper 08 is the combat engineer commander's level, and Sapper 11 is the combat engineer officer level. All IDF sappers are also trained as Rifleman 07, matching infantry.[ citation needed ]
In the Canadian Army, it is a term for soldiers that have completed the basic Combat Engineer training. 
In the Portuguese Army, a sapador de engenharia (engineering sapper) is a soldier of the engineering branch that has specialized combat engineer training. A sapador de infantaria (infantry sapper) is a soldier of the infantry branch that has a similar training and that usually serves in the combat support sapper platoon of an infantry battalion.
The Italian Army uses the term guastatori for their combat engineers.
In the Finnish army, pioneeri is the private equivalent rank in the army for a soldier who has completed the basic combat engineering training. Naval engineers retain the rank matruusi but bear the pioneeri insignia on their sleeves.[ citation needed ]
The German Bundeswehr uses the term Pionier for their combat engineers and other specialized units, who are associated with Special Forces to clear obstacles and perform engineering duties. Also the combat engineers in the Austro-Hungarian k.u.k. Forces were called "Pioniere".[ citation needed ]
In the British, Canadian, Australian and New Zealand armies, an assault pioneer is an infantry soldier with some limited combat engineer training in clearing obstacles during assaults and light engineering duties. Until recently, assault pioneers were responsible for the operation of flamethrowers.[ citation needed ]
Field engineer is a term used (or formerly used) in many Commonwealth armies. In modern usage, it is often synonymous with combat engineer. However, the term originally identified those military engineers who supported an army operating in the field instead of garrison engineers who built and supported permanent fixed bases. In its original usage, "field engineering" would have been inclusive of but broader than "combat engineering."[ citation needed ]
Sappers specialising in tunnel warfare may be known as miners.
In the French army, combat engineers specialising in bridge-building are pontoniers .
Combat engineers are force multipliers and enhance the survival of other troops through the use and practice of camouflage, reconnaissance, communications and other services. These include the construction of roads, bridges, field fortifications, obstacles and the construction and running of water points. In these roles, combat engineers use a wide variety of hand and power tools. They are also responsible for construction rigging, the use of explosives, and the carrying out of demolitions, obstacle clearance, and obstacle construction, assault of fortifications, use of assault boats in water obstacle crossings, helipad construction, general construction, route reconnaissance and road reconnaissance, and erecting communication installations. Combat engineers build and run water distribution points, carrying out water filtration, and NBC decontamination when necessary, and storage prior to distribution.[ citation needed ]
All these role activities and technologies are divided into several areas of combat engineering:
Improving the ability of one's own force to move around the battlefield. Combat engineers typically support this role through reduction of enemy obstacles which include point and row minefields, anti-tank ditches, wire obstacles, concrete, and metal anti-vehicle barriers, and improvised explosive devices (IED) and wall and door breaching in urban terrain. Mechanized combat engineer units also have armored vehicles capable of laying short bridges for limited gap-crossing.[ citation needed ]
Building obstacles to prevent the enemy from moving around the battlefield. Destroying bridges, blocking roads, creating airstrips, digging trenches, etc. Can also include planting land mines and anti-handling devices when authorized and directed to do so.[ citation needed ]
When the defender must retreat it is often desirable to destroy anything that may be of use to the enemy, particularly bridges, as their destruction can slow the advance of the attackers.
The placement of land mines to create minefields and their maintenance and removal.[ citation needed ]
Building structures which enable one's own soldiers to survive on the battlefield. Examples include trenches, bunkers, shelters, and armored vehicle fighting positions.[ citation needed ]
Defensive fortifications are designed to prevent intrusion into the inner works by 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.[ citation needed ]
Combat engineers employ a wide range of transportation vehicles and equipment and use weapons unique to the engineers, including those used in land mine warfare.
Basic combat engineering tools include safe use of:
For obstacle breaching, including minefields, the combat engineers use a variety of vehicles, explosive devices, and plastic explosives including:[ citation needed ]
The Basic Field Manual, Engineer Soldier's Handbook, 2 June 1943 (FM 21-105) was written to provide guidance to a new combat engineer in the United States. 
Military engineering is loosely defined as the art, science, and practice of designing and building military works and maintaining lines of military transport and military communications. Military engineers are also responsible for logistics behind military tactics. Modern military engineering differs from civil engineering. In the 20th and 21st centuries, military engineering also includes other engineering disciplines such as mechanical and electrical engineering techniques.
The term sapper is a historical term for a combat engineer that remains in use to describe certain personnel in various armies. The term is used, for example, in the armies of the United Kingdom and some Commonwealth nations and in the U.S. military.
The 130th Engineer Brigade is an engineer brigade of the United States Army headquartered in Schofield Barracks, Hawaii that provides engineering support to the United States Army Pacific. The brigade specializes in combat engineering, construction, and bridging operations.
The IDF Caterpillar D9 —nicknamed Doobi — is a Caterpillar D9 armored bulldozer used by the Israel Defense Forces (IDF). The Israeli armored CAT D9 was heavily modified by the Israel Defense Forces, Israeli Military Industries and Israel Aerospace Industries to increase the survivability of the bulldozer in hostile environments and enable it to withstand heavy attacks, thus making it suitable for military combat engineering use. The IDF Caterpillar D9 is operated by the Israel Defense Forces (IDF) Combat Engineering Corps for combat engineering and counter-terrorism operations.
Yahalom is a Sayeret unit of the Israeli Combat Engineering Corps of the Israel Defense Forces (IDF). The name "Yahalom" is an abbreviation of "Special Operations Engineering Unit".
The Israeli Combat Engineering Corps is the combat engineering forces of the Israel Defense Forces.
The anti-personnel obstacle breaching system (APOBS) is an explosive line charge system that allows safe breaching through complex antipersonnel obstacles, particularly fields of land mines. The APOBS is a joint DOD program for the U.S. Army and the United States Marine Corps.
An Assault Pioneer is an infantry soldier who is responsible for:
The armored bulldozer is a basic tool of combat engineering. These combat engineering vehicles combine the earth moving capabilities of the bulldozer with armor which protects the vehicle and its operator in or near combat. Most are civilian bulldozers modified by addition of vehicle armor/military equipment, but some are tanks stripped of armament and fitted with a dozer blade. Some tanks have bulldozer blades while retaining their armament, but this does not make them armored bulldozers as such, because combat remains the primary role — earth moving is a secondary task.
The 9th Engineer Battalion is a unit of the United States Army that deploys to designated contingency areas and conducts combat and/or stability operations in support of a brigade combat team. It is a divisional mechanized combat engineer unit, composed of three line companies and a headquarters company. Its mission is to provide assured mobility, counter-mobility, general engineering, and survivability support, with well trained sappers ready to deploy anywhere at any time. The unit's history spans service in 1917 in the US southwest, World War II in France and Germany, multiple deployments to the Balkans, and multiple deployments in support of the Global War on Terrorism in Iraq and Afghanistan. It is most famous for the capture of the Ludendorff Bridge across the Rhine River. As of 18 May 2015, the battalion exists as the 9th Brigade Engineer Battalion in Fort Stewart, GA under 2nd Armored Brigade Combat Team, 3rd Infantry Division.
The 1st Engineer Battalion is a unit of the United States Army with a record of accomplishment in both peace and war; an organization that provides sustained engineer support across the full spectrum of military operations. The 1st Engineer Battalion is the oldest and most decorated engineer battalion in the US Army, tracing its lineage to the original Company of Sappers and Miners organized at West Point, New York in 1846.
The 31 Company of Engineers was an Irish Defence Forces Engineering Support Company under the command of the Southern Reserve Brigade.
The Indian Army Corps of Engineers is a combat support arm which provides combat engineering support, develops infrastructure for armed forces and other defence organisations and maintains connectivity along the borders, besides helping the civil authorities during natural disasters. College of Military Engineering, Pune (CME) is the premier technical and tactical training institution of the Indian Army Corps of Engineers.
Armoured Vehicle Royal Engineers (AVRE), also known as Assault Vehicle Royal Engineers is the title given to a series of armoured military engineering vehicles operated by the Royal Engineers (RE) for the purpose of protecting engineers during frontline battlefield operations.
A pioneer is a soldier employed to perform engineering and construction tasks. The term is in principle similar to sapper or combat engineer.
The 107th Engineer Battalion is a large unit of the Michigan Army National Guard stationed in Ishpeming Michigan. The unit operates in the Upper Peninsula of Michigan and is composed of the Headquarters Company stationed in Ishpeming and 1430th, 1431st, 1432nd, and 1437th Engineer Companies which are stationed across other various cities in Northern Michigan with the battalion headquarters in Ishpeming, Michigan. The 507th Engineer Battalion of the Michigan National Guard is regarded as the sister unit to the 107th because if consists of the same elements but is headquartered in the lower peninsula. The unit's motto is "Good as Done!"
The School of Engineers is part of the South African Army Engineer Formation, which provides combat engineering corps training and teaching to military officers and personnel as well as other Military Schools throughout the South African National Defence Force. They are currently the only Military School in Southern Africa to formally present IEDD.
The Engineer Troops of the Russian Federation are a military administrative corps of the Ground Forces of the Russian Federation designed to perform military engineering operations, requiring special training of personnel and use of means of engineer equipment, as well as for damaging the enemy through application of engineer ammunition.
Engineer Troops of the USSR — were special troops of the Soviet Armed Forces, designed for military engineer support: combat operations; engineering reconnaissance, and escort of troops (forces) in the offensive, and so on.