The Power Rangers phenomenon began in 1993 with the US television debut of the uniquely campy Mighty Morphin' Power Rangers.  An instant success among boys age 7 to 12, Power Rangers treated its audience to messages of cooperation and nonviolence interspersed with healthy portions of Japanese footage featuring spandex-clad, helmeted superheroes blowing up rubber monsters with guns, swords, and giant robots.  Setting the standard for American live action children's entertainment, the show owed much of its popularity to elements borrowed from the Japanese action genre known as Super Sentai, where years of experimentation had resulted in a string of yearly serials packed with drama, superheroes, monsters, and robots.

The term "sentai," meaning "task force," refers to a team of color-coded, costumed superheroes - generally five - who battle a sinister presence bent on conquering the world with hordes of generic foot soldiers and weekly monsters.  But although sentai dates back to 1975's Goranger, its traditions have themselves been borrowed from prior works within the Japanese category of filmmaking known as tokusatsu.  What follows is a series of tokusatsu milestones which have contributed to make sentai what it is today.

Gojira (Godzilla) - 1954

An allegory for the threat of American atomic power, Godzilla marked the dawn of the daikaijuu (giant monster) era, as well as the birth of tokusatsu in general.  It featured the first use of a costumed actor in a miniature city set.

Supergiant - 1957

The first tokusatsu superhero, Supergiant was Japan's answer to Hollywood's Adventures of Superman (1952).  The show was dubbed for Western audiences as Starman.

Gekko Kamen (Moonlight Mask) - 1958

Although devoid of superpowers, Gekko Kamen was the first masked tokusatsu hero.

Marine Kong - 1960
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Marine Kong, a somewhat cute-looking giant creature with robotic insides, was the protagonist of the first tokusatsu TV series to feature a new giant monster in each episode.

Tetsujin 28 (Iron Man 28) - 1963

Dubbed in the West as Gigantor, Tetsujin 28 was the first giant robot.  Although anime (Japanese animation), this series would serve as inspiration for future giant robots in tokusatsu.

Ultra Q - 1966

Somewhat reminiscent of The Twilight Zone (1959), Ultra Q told the tale of human officers pitted against a new giant monster each episode.  The series which popularized serial daikaijuu, Ultra Q also introduced numerous monsters which would be reused in Ultraman (1966).

Magma Taishi (Ambassador Magma) - 1966

Ambassador Magma, a giant hero who transformed into a rocket, was the first giant tokusatsu hero on television, beating Ultraman to the air by less than two weeks.  In the US dub, Space Giants, the hero was known as "Goldar," which was also the Power Rangers name for Grifforzar of Zyuranger (1992).

Ultraman - 1966

Hugely popular and spawning innumerable sequels, Ultraman was the first enlarging hero to grow from human size to giant proportions.  His nemeses were generally daikaijuu who were already giant themselves.

Giant Robo - 1967

Similar to Tetsujin 28, Giant Robo featured a giant robot controlled remotely by a young boy to battle giant monsters.  Known in the West as Johnny Sokko and His Flying Robot, the show was liberally remade into an anime release in 1991.

Spectreman - 1971

Although not a milestone, Spectreman was a hit show which heralded a second wave of giant heroes.  Additionally, the show's super-intelligent simian mastermind, Dr. Gori, was apparently the basis for Mojo Jojo of The Powerpuff Girls (1998).

Kamen Rider - 1971

A milestone equal in importance to Ultraman (1966), Kamen Rider introduced the henshin hero genre, in which the protagonist is able to transform ("morph," in Power Rangers) from human to superhero form and then back again.  One of Kamen Rider's many sequels, Kamen Rider Black RX (1988), would be adapted in the United States as Saban's Masked Rider (1995).

Gatchaman - 1972

An anime dubbed repeatedly for the US market (Battle of the Planets in 1978, G-Force in 1986, and Saban's Eagle Riders in 1996), Gatchaman set the standard for the five-person hero dynamic featured throughout sentai.

Mazinger Z - 1972

Dubbed in the West as Tranzor Z, Mazinger Z was the first internally piloted giant robot, effectively launching a craze over such robots which would spread from anime to tokusatsu.  The series spawned several sequels.

Getter Robo - 1974

Another giant robot anime, Getter Robo featured the first robot to combine from multiple components.  This trend would soon spread to tokusatsu.

Himitsu Sentai Goranger (Secret Task Force GoRanger) - 1975

Featuring five caped, color-coded, and helmeted superheroes, Goranger was the first sentai series.  Armed with a slew of vehicles, the Gorangers battled human-sized monsters in the tradition of Kamen Rider (1971).  The series aired through 1977, the longest-running sentai series to date.

Combattler V - 1976

Yet another giant robot anime, Combattler V featured the first five-piece combining robot.  Its character design resembles both Gatchaman (1972) and GoLion (1981).

JAKQ Dengekitai (JAKQ Blitzkrieg Squad) - 1977

An initially dark series featuring a four-person team, JAKQ was given a lighter tone with the introduction of Big One, the first additional member to a sentai team.  Like its predacessor Goranger, the JAKQ team was caped and had no mouthplate designs.

Spiderman - 1978

A Japanese tokusatsu series based on the Marvel Comic, Spiderman featured the web-slinger pitted against human-sized monsters who grew to giant size upon being defeated.  Spiderman then faced off with his foes a second time, piloting his giant robot Leopardon.  This introduced what would become the standard Super Sentai formula featuring monster battles on two scales in the same episode.

Battle Fever J - 1979

An attempt to recapture the popularity of Spiderman (1978), Battle Fever J was the first Super Sentai, featuring a five-man sentai team which faced monsters in both human and giant sizes, with the assistance of a giant robot.  Originally based on Marvel's Captain America, the series starred Battle Japan and teammates.  Designed after Captain America's costume, the metal mouthplates introduced in Battle Fever J would remain a recurring element of sentai to come, albeit without the noses.

Daltanias - 1979

A giant robot anime, Daltanias introduced an animal design for one of its robot components.  The lion theme would later take off in the 1981 anime GoLion.

Denshi Sentai Denjiman (Electronic Task Force Denziman) - 1980

The first traditional-looking Super Sentai, Denjiman introduced the familiar sentai goggle masks, as well as sentai's first transforming giant robot.  The series returned to the prominent use of color-coded costumes and names established in Goranger (1975), although the scarves from Battle Fever J (1979) remained.  Its abstract mouthplate designs were likely inspired by Kamen Rider.

Taiyou Sentai Sunvulcan (Solar Task Force Sunvulcan) - 1981

The first (and only) sentai to continue from the previous series, Sunvulcan also featured the first combining sentai robot, as well as the first animal-themed sentai heroes.  It was also the sentai with the smallest number of heroes.

GoLion - 1981

A widely popular sentai-based anime dubbed as Voltron in the West, GoLion popularized the animal-based robot components.  Tied for American viewers with an originally unrelated anime, Dairugger XV (Vehicle Voltron), the Voltron franchise served as many Westerners' first experience with sentai elements such as the five-man costumed team and the combining robot pitted against giant monsters.  Voltron returned in a CGI American sequel in 1998.

Uchuu Keiji Gavan (Space Sheriff Gavan) - 1982

The first "Metal Hero" show, Space Sheriff Gavan spawned such sequels as Uchuu Keiji Shaider (Space Sheriff Shaider, 1984), Jikuu Senshi Spielban (Dimensional Warrior Spielban, 1986), and Cho Jinki Metalder (Superhuman Machine Metalder, 1987), all of which were used for Saban's VR Troopers (1994), as well as Juukou B-Fighter (Heavy Armor B-Fighter, 1995) and B-Fighter Kabuto (1996), which were adapted into Saban's Big Bad Beetleborgs (1996) and Beetleborgs Metallix (1997).

Kagaku Sentai Dynaman (Science Task Force Dynaman) - 1983

The first sentai with traditional shiny spandex suits in place of cloth, Dynaman was later dubbed as a six-episode comedy of the same name on the USA Network in 1988.  For many viewers of USA's "Night Flight" segment, Dynaman was a first glimpse into the world of sentai.

Hikari Sentai Maskman (Light Task Force Maskman) - 1987

Following popular trends established in anime, Maskman featured the first five-piece sentai robot.  Additionally, for a single episode, it became the first sentai with a sixth member.

Chojuu Sentai Liveman (Super Beast Task Force Liveman) - 1988

Initially consisting of only three heroes like 1981's Sunvulcan, Liveman later introduced an additional two heroes, a strategy repeated in 2002's Ninpuu Sentai Hurricanger (Ninja Sentai Hurricanger).  Liveman was also the first sentai with animal-based robots.

Kosoku Sentai Turboranger (High Speed Task Force Turboranger) - 1989

Similar in concept to Saban's Mighty Morphin' Power Rangers (1993), Turboranger reintroduced the term "Ranger," which had not been used since 1975's Goranger.  Connoting a roving combat squadron, the term would be used by nearly all future sentai seasons, as well as Saban's Power Rangers adaptations.

Chojin Sentai Jetman (Birdman Task Force Jetman) - 1991

An homage to the 1972 anime Gatchaman, Jetman was a dark drama which producer Haim Saban attempted to pitch for Western audiences.  He would not succeed until the following year with 1992's Zyuranger.

Kyoryuu Sentai Zyuranger (Dinosaur Task Force Zyuranger) - 1992

Zyuranger was the first sentai successfully adapted by Saban Entertainment.  Used as source material for 1993's Mighty Morphin' Power Rangers, the show's multicolored heroes and robot dinosaurs were a hit with Western audiences.  Each successive sentai series from this point forward would be adapted into a new season of Power Rangers, introducing new villains and weaponry within an ongoing continuity not ordinarily found within the world of sentai.  In addition to its significance to the Power Rangers phenomenon, Zyuranger was also the first sentai which featured a recurring sixth Ranger.

Choriki Sentai Ohranger (Super Task Force Ohranger) - 1995

1995's Ohranger began the tradition of a crossover movie featuring the current and previous sentai teams side-by-side - in this case, Ohranger vs. Kakuranger ("versus" generally signifying a teamup rather than a battle).  Ohranger also marked the beginning of Saban's more intensive use of sentai, as the suits and villains derived from Zyuranger were finally replaced in the 1996 Ohranger adaptation, Power Rangers Zeo.  Each successive season of Power Rangers would see the introduction of new powers, villains, and a new series title.