Seeking documentation about the history of the United States' relation with the native Americans he read about the Wounded Knee Massacre, and used it as a starting point for his stories.
Similarly to revisionist Western, he tried to avoid the standard portrayal of the cowboy as a flawless hero, and made him instead a man trying to make amends for the killing of natives.
An additional Sargento Kirk story was published in 1973 in the magazine Billiken, drawn by Gustavo Trigo.
[5] Sergeant Kirk is a former soldier of the American Civil War who goes on to serve in the post-war Wild West.
[6] Among Kirk's companions appearing in the series are "El Corto", Dr. Forbes and the Native American boy, Maha.