John Dean "Jeff" Cooper (May 10, 1920 – September 25, 2006) was a United States Marine and firearms instructor.

During World War II he served in the Pacific theater with the Marine Detachment aboard USS Pennsylvania.

He resigned his commission in 1949 but returned to active duty during the Korean War, where he claimed to be involved in irregular warfare in Southeast Asia,[5] and was promoted to lieutenant colonel.

[1] In 1976 Cooper founded the American Pistol Institute (API) in Paulden, Arizona (later the Gunsite Academy).

Cooper began teaching shotgun and rifle classes to both law enforcement and military personnel, as well as civilians, and conducted on-site training for individuals and groups from around the world.

In Orange you have determined upon a specific adversary and are prepared to take action which may result in his death, but you are not in a lethal mode.

[9]The color code, as originally introduced by Cooper, had nothing to do with tactical situations or alertness levels, but rather with one's state of mind.

It is equally useful in securing meat for the table, destroying group enemies on the battlefield, and resisting tyranny.

Cooper defined his goal: a general-purpose rifle is a conveniently portable, individually operated firearm, capable of striking a single decisive blow on a live target of up to 200 kilos in weight at any distance at which the operator can shoot with the precision necessary to place a shot in a vital area of the target.

[17][18][19][20][21] Cooper was dissatisfied with the small-diameter 5.56×45mm NATO (.223 Remington) of the AR-15 and envisioned a need for a large-bore (.44 caliber or greater) cartridge in a semi-automatic rifle to provide increased stopping power and one-shot kills on big-game animals at 250 yards.

The so-called Thumper concept inspired the development of the .450 Bushmaster, .458 SOCOM, .458 HAM'R, .499 LWR, and the .50 Beowulf, among other cartridges, all suitable for integration into the AR-15/M16 rifle/M4 carbine or AR-10/M14 rifle platforms.

[22] In 1997, Cooper wrote that he coined the term hoplophobia in 1962 "in response to a perceived need for a word to describe a mental aberration consisting of an unreasoning terror of gadgetry, specifically, weapons.

"[23] In addition to his books on firearms and self-defense, Cooper wrote several books recounting his life adventures plus essays and short stories, including Fire Works (1980); Another Country: Personal Adventures of the Twentieth Century (1992); To Ride, Shoot Straight and Speak the Truth (1988); and C Stories (2004).

These were his thoughts on firearms interleaved with his wide-ranging musings on many other subjects and acquired a large U.S. and international following from the 1980s up to his death.

In 1991, Cooper wrote in Guns & Ammo magazine that "no more than five to ten people in a hundred who die by gunfire in Los Angeles are any loss to society.