Killer Junior and Killer Senior are techniques of employing artillery

Artillery

Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...

 direct fire

Direct fire

Direct fire refers to the launching of a projectile directly at a target on a relatively flat trajectory. The firing weapon must have a sighting device and an unobstructed line of sight to the target, which means no objects or friendly units can be between it and the target...

 air burst

Air burst

An air burst is the detonation of an explosive device such as an anti-personnel artillery shell or a nuclear weapon in the air instead of on contact with the ground or target or a delayed armor piercing explosion....

s, first developed during the Vietnam War

Vietnam War

The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

. The technique involves a howitzer or gun firing a high explosive (HE) shell fuzed with a mechanical time-super quick (MTSQ) artillery fuse set to function causing an airburst over a target in very close proximity to the gun

Gun

A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...

's position. Set properly, the shell would detonate approximately 10 meters (30 feet) above the ground at ranges of 200 to 1000 meters.

The term Killer Junior was applied to this technique when used with 105mm or 155mm howitzers, and the term Killer Senior applied to its use with the M115 203mm (8-inch) howitzer

M115 203 mm howitzer

The M115 203 mm howitzer, also known as the M115 8 inch howitzer, was a towed howitzer used by the United States Army. Originally designated the 8 inch Howitzer M1, it was designed during the buildup to World War II as a counterpart to the German 17 cm K 18 gun...

. The term "Killer" came from the call-sign of the battery which developed the technique. The technique was later perfected by Lieutenant Colonel Robert Dean, commander of the 1st Battalion, 8th Field Artillery, of the 25th Infantry Division Artillery.

Killers Junior and Senior were developed as alternatives to the Beehive

Beehive (ammunition)

Beehive is an anti-personnel round fired from an artillery gun. The round is packed with metal flechettes which are ejected from the shell during flight by a mechanical time fuze. It is so called because of the 'buzzing' sound the darts make when flying through the air...

 flechette

Flechette

A flechette is a pointed steel projectile, with a vaned tail for stable flight. The name comes from French , "little arrow" or "dart", and sometimes retains the acute accent in English: fléchette.-Bulk and artillery use:...

 rounds previously used against nearby enemy troops. The advantage of Killer Junior over beehive is that the airburst projects fragments in all directions, and is able to wound enemy crawling or lying in defilade

Enfilade and defilade

Enfilade and defilade are concepts in military tactics used to describe a military formation's exposure to enemy fire. A formation or position is "in enfilade" if weapons fire can be directed along its longest axis. A unit or position is "in defilade" if it uses natural or artificial obstacles to...

, whereas the flechettes of a Beehive round would simply fly harmlessly over a low target.

Source

• Major General David Ewing Ott. FIELD ARTILLERY, 1954-1973. Department of the Army. Washington D.C., 1975.