Revolutionary War general Casimir Pulaski was dubbed the “Father of the American Cavalry” in a presidential proclamation last October, but an upcoming documentary will show research suggesting Pulaski may have been female or intersex.

Researchers have examined remains believed to be Pulaski's and used skeletal evidence to document the case that Pulaski, who lived as a man, may have been a woman or an intersex individual — a person who has both female and male biological characteristics.

The Smithsonian Channel will premiere a documentary about the research — "America’s Hidden Stories: The General Was Female?" — on April 8 at 8 p.m.

Pulaski's legacy as a war hero was highlighted in a proclamation by President Donald Trump declaring Oct. 11, 2018, as General Pulaski Memorial Day. The proclamation says Pulaski once saved Gen. George Washington in battle and that Pulaski transformed a calvary legion of Americans and allies into a "lethal fighting force."

Pulaski died during the Battle of Savannah and has since secured a legacy as a Polish-American hero, with numerous towns, schools and roads named after the general, as documented by NBC News.

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The evidence that Pulaski may not have been a man comes primarily from a skeletal analysis.

“One of the ways that male and female skeletons are different is the pelvis,” Virginia Hutton Estabrook, a contributor to the documentary and an assistant professor of anthropology at Georgia Southern University told NBC News. “In females, the pelvic cavity has a more oval shape. It’s less heart-shaped than in the male pelvis. Pulaski’s looked very female.”

The female characteristics were so striking that some experts originally believed that the skeleton could not have belonged to Pulaski, the documentary says.

In "The General Was Female?" researchers work to definitively link the remains to Pulaski. They also say the skeletal record is consistent with an individual who rode horses and sustained battle injuries.

The film portrays Pulaski as a solitary, charismatic and driven individual. Those characteristics have helped shape the general's legacy, but also closely mirror how an intersex individual may have lived during that period in history, filmmakers suggest.

The Intersex Society of North America says about 1 in 1,500 to 2,000 children are known to be intersex at birth but more find sex anatomy variations later in life.