While its name derives from the name of Raoul Lufbery, the leading fighter ace of the Lafayette Escadrille, he did not invent the tactic; how it acquired this name is not known, although it may be from his popularization of it among the incoming U.S. pilots he trained. In non-American sources it is in fact usually referred to simply as a "defensive circle".
This air tactic can only be mounted by formations of aircraft working together: it involves forming a horizontal circle in the air when attacked, in such a way that the armament of each aircraft offers a measure of protection to the others in the circle. It complicates the task of an attacking fighter - the formation as a whole has far fewer "blind spots" than its members, so that it is more difficult to attack an individual aircraft without being exposed to return fire from the others.
Perhaps the earliest use of the tactic was by formations of F.E.2b aircraft in 1916/17 when in combat with superior German fighters; even by the end of World War I it was considered flawed and obsolete. The Lufbery circle, while generally effective against horizontal attacks by faster aircraft, was very vulnerable to attacks from fighters diving from above, providing targets on a slow, predictable course. As the performance and armament of fighter aircraft improved during the First World War they became capable of high-speed hit-and-run attacks in the vertical; a Lufbery would put the defenders at a gross disadvantage.
In World War II the Lufbery was still used by many countries, generally as a last resort measure for poorly trained pilots of less advanced air forces - for instance, Japanese kamikaze pilots. Faster allied aircraft resulted in the more manoeuvrable Zero also resorting to the tactic to lure opponents into a turning contest in which the Zero could prevail. This tactic was also used by German Messerschmitt Bf 110 fighters, which had a rearwards-firing dorsal gun position, and British Boulton Paul Defiant fighters, with dorsal turrets, during the Battle of Britain.
Lundstrom, in chronicling the operational history of US carrier-based activities in the Pacific from Pearl Harbor through the Battle of Midway, provides an extensive discussion of fighter tactics of the time. In the Battle of the Coral Sea, US Grumman F4F Wildcats defending the USS Lexington against Japanese dive bombers adopted a Lufbery Circle when attacked by A6M Zeros.
Although the Lufbery would seem to expose modern aircraft to missiles and unchecked gunnery passes, US pilots in the Vietnam War found North Vietnamese MiG-17 fighters using it as bait for faster F-4 Phantom fighters that did not have guns and could not use their missiles because of tight turns made by the MiGs.
Other uses of the term
Mostly in World War II literature, a Lufbery Circle can be used to refer to any turning engagement between aircraft, i.e. what is more properly known as the Turn Fight in air combat tactics.
In modern discussions of air-to-air combat tactics, a "Lufbery" generally refers to any prolonged horizontal engagement between two fighters with neither gaining the advantage. This frequently occurs when both fighters have descended to low altitude and have insufficient energy for further vertical maneuvering, thus restricting the fight to the horizontal plane. Such a fight assumes that one fighter does not have a significant turn rate advantage and is thus locked in a seemingly endless tail chase.
Such a fight is said to wind up in a Lufbery or has said to have "Luffed out"; this being a generally undesirable circumstance as neither fighter is able to conclude the fight nor leave without potentially exposing himself to attack by the remaining fighter.
- pp. 255-256 and pp.353, 481, Lundstrom; discusses the Lufbery Circle in the context of the subsequently developed Thach Weave.