Is the movie based on the Second Franco-Dahomean War?
https://en.wikipedia.org/wiki/Second_Franco-Dahomean_War
This unusual emergence of an all-female military regiment was the result of Dahomey's male population facing high casualties in the increasingly frequent violence and warfare with neighbouring West African states, which led to Dahomey being forced to annually give male slaves to particularly the Oyo Empire, which used that for commodity exchange as part of the growing phenomenon of slave trade in West Africa during the Age of Discovery. The lack of men likely led the kings of Dahomey to recruit women into the army.
In 1889, King Glele died and his son Béhanzin came to power and immediately became quite hostile to the French in negotiations. Béhanzin renounced the treaty with France providing them with the city of Cotonou and began raiding the possessions. The hostility hit a high point when Béhanzin began conducting slave raids in French protectorates along the coast, namely Grand-Popo, in 1891. That year, the French military decided that a military takeover was the only solution and placed General Alfred-Amédée Dodds in charge of the operation to commence in 1892.
The Franco-Dahomean War lasted from 1892 until January 1894 when Dodds captured the city of Abomey (January 15) and King Béhanzin (January 25). Notable during the war was the defeat of the Dahomey Amazons in November 1892. Dodds named Agoli-agbo the new king of Dahomey, largely because he was seen as the most malleable of the alternatives, and exiled Béhanzin to French possessions in the Caribbean. The French began changing key aspects of administration and politics in the Kingdom of Dahomey. In 1899, the French instituted a new poll tax which was highly unpopular and Agoli-Agbo opposed the tax causing serious political problems in the protectorate. As a result, on February 17, 1900, the French deposed Agoli-Agbo and ended the Kingdom of Dahomey. The French though brought together many key members of the kingdom as the chiefs of cantons. French Dahomey included the Kingdom of Dahomey, with Porto-Novo and an area to the north of loose tribal control.
That's the only time where I read Amazons were involved (excluding the one major battle in the first war). As you can see by the battle result, the African Kingdom of Dahomey and its warriors got creamed HARD in the thousands while French loses were minimal and below 500. Most of the loses came from hand-to-hand combat where they lost to bayonets.
Funny how they TOO were dealing in the slave trade but all Western nations recognize is just the whites doing so. British tried to put a diplomatic end to it but the king refused with the eventual blockade by the British to force an end to it.
https://en.wikipedia.org/wiki/History_of_the_Kingdom_of_Dahomey#Suppression_of_the_slave_trade_(1852-1880)
It'll be interesting how they'll fantasize this movie to make it like the Amazons were kicking hardcore ass against the French.