Indirect fire in the context of Line of sight

A spitzer bullet (from German Spitzgeschoss 'point shot') is a munitions term, primarily regarding fully-powered and intermediate small-arms ammunition, describing bullets featuring an aerodynamically pointed nose shape, called a spire point, sometimes combined with a tapered base, called a boat tail (then a spitzer boat-tail bullet), in order to reduce drag and obtain a lower drag coefficient, resulting in an aerodynamically superior torpedo shaped projectile, which decelerates less rapidly and has improved external ballistic behaviour, at the expense of some potential weight and kinetic energy relative to blunter ogive/round/flat-nose flat-base projectiles.

The type was developed for military purposes in the late 19th and early 20th century and was a major design improvement compared to earlier rounder or flatter-tipped bullets in terms of range and accuracy. Its introduction, along with long-range volley sights for service rifles, changed military doctrines. Area targets at ranges up to 1,420–2,606 m (1,550–2,850 yd) could be subject to rifle fire. With improvements in machine guns at the turn of the 20th century, the addition of clinometers meant that fixed machine gun squads could deliver plunging fire or indirect fire at more than 3,000 m (3,280 yd). The indirect firing method exploits the maximal effective range, that is defined by the maximum range of a small-arms projectile while still maintaining the minimum kinetic energy required to put unprotected personnel out of action, which is generally believed to be 15 kilogram-meters (147 J / 108 ft⋅lbf).

An artillery observer, artillery spotter, or forward observer (FO) is a soldier responsible for directing artillery and mortar fire support onto a target. An artillery observer usually accompanies a tank or infantry unit. Spotters ensure that indirect fire hits targets which those at a fire support base cannot see.

A mortar today is usually a simple, lightweight, man-portable, muzzle-loaded cannon consisting of a smooth-bore (although some models use a rifled barrel) metal tube fixed to a base plate (to spread out the recoil) with a lightweight bipod mount and a sight. Mortars are typically used as indirect fire weapons for close fire support with a variety of ammunition. Historically, mortars were heavy siege artillery. Mortars launch explosive shells (technically called bombs) in high arching ballistic trajectories.

The formal definition of large-calibre artillery used by the United Nations Register of Conventional Arms (UNROCA) is "guns, howitzers, artillery pieces, combining the characteristics of a gun, howitzer, mortar, or rocket, capable of engaging surface targets by delivering primarily indirect fire, with a calibre of 76.2 mm (3.00 in) and above". This definition, shared by the Arms Trade Treaty and the Treaty on Conventional Armed Forces in Europe, is updated from an earlier definition in United Nations General Assembly Resolution 46/36L, which set a threshold of 100 mm (3.9 in). Several grammatical changes were made to that latter in 1992 and the threshold was lowered in 2003 to yield the current definition, as endorsed by UN General Assembly Resolution 58/54.

Historically, large-calibre weapons have included bombards and siege guns.

Direct fire or line-of-sight fire refers to shooting of a ranged weapon whose projectile/ordnance is launched directly at a target within the line-of-sight of the user. Direct fire weapons typically have a sighting device to ensure accuracy and must have an unobstructed view to the target with no obstacles or friendly units in between, meaning that they can only effectively engage targets that are in enfilade. Conversely, direct fire units are also directly exposed to return fire from the target unless they are shooting from a position of defilade or concealment.

Direct fire is in contrast to indirect fire, which refers to firing a projectile on a curved ballistic trajectory or delivering self-accelerated munitions capable of long range and various degrees of homing abilities to alter the flight path. Indirect fire does not need a direct line-of-sight to the target because the shots are normally directed by a forward observer who provides the coordinates and calibrations needed to hit the target. As such, indirect-fire weapons can shoot over obstacles or friendly units and the weapons can be concealed from counter-battery fire.

Fire support is a military tactics term used to describe the use of weapons and munitions aimed to support friendly forces by engaging, destroying or suppressing enemy forces, facilities, or materiel in combat. It is often provided through indirect fire (artillery) launched from the rear, though the term may also be used for some direct fire or aerial attacks performed by front line units to support other friendly units.

The United States Department of Defense defines fire support as "fires that directly support land, maritime, amphibious, and special operations forces to engage enemy forces, combat formations, and facilities in pursuit of tactical and operational objectives."

Plunging fire is a form of indirect fire, where gunfire is fired at a trajectory to make it fall on its target from above. It is normal at the high trajectories used to attain long range, and can be used deliberately to attack a target not susceptible to direct or grazing fire due to not being in direct line of sight.

In naval warfare, plunging shellfire was theoretically capable of penetrating an enemy ship's thinner deck armor rather than firing directly at a warship's heavily armored side.

In military usage, a barrage is massed sustained artillery fire (shelling) aimed at a series of points along a line. In addition to attacking any enemy in the kill zone, a barrage intends to suppress enemy movements and deny access across that line of barrage. The impact points along the line may be 20 to 30 yards apart, with the total line length of the barrage zone anything from a few hundred to several thousand yards long. Barrages can consist of multiple such lines, usually about 100 yards apart, with the barrage shifting from one line to the next over time, or several lines may be targeted simultaneously.

A barrage may involve a few or many artillery batteries, or even (rarely) a single gun. Typically each gun in a barrage, using indirect fire, will fire continuously at a steady rate at its assigned point for an assigned time before moving onto the next target, following the barrage's detailed timetable. Barrages typically use high-explosive shells, but may also be shrapnel, smoke, illumination, poison gas (in World War I), or potentially other chemical agents. Barrages are in contrast with concentrated artillery fire, which has a single specific target such as a known enemy position or structure, and in contrast with direct fire which targets enemies within the direct line of sight of the gun.

In field artillery, the accuracy of indirect fire depends on the use of aiming points. In air force terminology the aiming point (or A.P.) refers to holding the intersection of the cross hairs on a bombsight when fixed at a specific target.

An indirect fire aiming point provides a point of angular reference to aim a gun in the required horizontal direction – azimuth. Until the 1980s aiming points were essential for indirect fire artillery. They are also used by mortars and machine guns firing indirectly.

Special reconnaissance (SR) is conducted by small units, such as a recon team, made up of highly trained military personnel, usually from special forces units and/or military intelligence organizations. Special reconnaissance teams operate behind enemy lines, avoiding direct combat and detection by the enemy. As a role, SR is distinct from commando operations, but both are often carried out by the same units. The SR role frequently includes covert direction of airstrikes and indirect fire, in areas deep behind enemy lines, placement of remotely monitored sensors, and preparations for other special forces. Like other special forces, SR units may also carry out direct action and unconventional warfare, including guerrilla operations.

In intelligence terms, SR is a human intelligence (HUMINT) collection discipline. Its operational control is likely to be inside a compartmented cell of the HUMINT, or possibly the operations, staff functions. Since such personnel are trained for intelligence collection as well as other missions, they will usually maintain clandestine communications to the HUMINT organization and will be systematically prepared for debriefing. They operate significantly farther forward than even the most forward friendly scouting and surveillance units.

In military tactics, the kill zone, also known as killing zone, is an area entirely exposed to effective direct fire or accurately zeroed indirect fire, typically as an element of ambush within which an approaching enemy force is encircled/flanked, engaged and destroyed. The objective of the ambushing force is to seize the element of surprise to quickly kill or capture all hostile combatants inside the kill zone, and the ambushed soldiers (who may or may not be trapped) may respond by counterattacking and/or breaking out of the kill zone.

The term is also used in non-lethal sense in military exercises and simulations, as well as in recreational wargaming and MilSim shooting sports such as paintball, airsoft and laser tag, as a region within the training area, playing field or arena where intense shootouts and elimination of participants are most likely to happen.

A reverse slope defence is a military tactic where a defending force is positioned on the slope of an elevated terrain feature such as a hill, ridge, or mountain, on the side opposite from the attacking force. This tactic both hinders the attacker's ability to observe the defender's positions and reduces the effectiveness of the attacker's long-range weapons such as tanks and artillery.

A defending unit usually does not conduct a reverse-slope defence along its entire front, as positioning troops on the forward slope is necessary to control the region in front of the hill. However, when enemy forces are known to have superior long-range direct-fire or indirect-fire weapons, the majority of the defending force can use the hill to limit enemy observation and reduce the effectiveness of the long-range enemy fire. This tactic may even succeed in deceiving the enemy as to the true location and organisation of the main defensive positions. Typically, a smaller unit is still posted on the forward slope to perform observation and delay attackers if the defending force needs to relocate its main body onto the forward slope. Otherwise, when the attacker advances and passes over the top of the hill, they may be ambushed by short-range fire from the defender on the reverse slope and perhaps on the counterslope (the forward slope of a hill facing the reverse slope). Combat vehicles are vulnerable when cresting hills, because their thin belly armour may be exposed to troops on the reverse slope and because their weapons may lack the depression angle to effectively engage an enemy located below the vehicle.