Blackhawk, leader of the Blackhawk Squadron, first appeared in Military Comics (Quality Comics, 1941 Series) #1 (August 1941).
Blackhawk's origin story has changed over the years, sometimes significantly. In Military Comics #1, his brother Jack and sister Connie were killed in a farmhouse in Poland in 1939, when the building was bombed by Captain von Tepp. A text feature in Blackhawk (Quality Comics, 1944 series) #50 (March 1952) revealed that Blackhawk was an American who was a voluntary flyer in the Polish Air Force in 1939, but no mention is made of his siblings or Captain von Tepp. This feature was reprinted in issues #93 and #107 with slight alterations, and in #164 with more significant changes. In issue #71 (December 1953), Blackhawk is again said to be an American, however his brother is now named Charlie and is a doctor, and his sister is an unnamed nurse. Captain Von Tepp leads a squadron which bombs the Army hospital that Blackhawk's siblings are volunteering at, then shoots them when they flee the building. The origin story is drastically altered in Blackhawk (DC, 1957 series) #198 (July 1964), where it is established that the Blackhawks' first mission didn't occur until D-Day (June 1944); Blackhawk's siblings and Captain Von Tepp are completely removed from this origin. Blackhawk's origin is again radically changed in issue #242 (August-September 1968). His real name is given as "Bart Hawk" for the first and only time, and in this version of the story, his brother Jack Hawk (using the alias Jack Dawson) crashed while flying a drone on a mission with Bart. Jack was believed to have been killed, but survived and returned years later as Black Mask. When Mark Evanier revived the series in issue #251 (October 1982), he returned the origin story to its roots. Once again, Captain von Tepp was responsible for the deaths of Blackhawk's siblings, Jack and Connie, when he ordered the bombing that destroyed their house in Poland in 1939.
Blackhawk was given a secret identity in only a handful of stories. In Blackhawk (DC, 1957 series) #184 (May 1963), he tells a boy his name is Bart Hawks (with an "s"), however in the context of the story this could be an alias. Then in issue #242 (August-September 1968), he was given the name Bart Hawk. Although this is clearly stated to be his real name, the story itself contradicts all previous and subsequent stories and cannot be considered canon. The letters page of issue #244 (January-February 1976) explicitly stated that "Bart Hawk" is an alias, and that Blackhawk's true name is unknown. This issue also introduced Blackhawk's alias of "Mr. Cunningham". No mention was made of "Bart Hawk" during Mark Evanier's run, which began in issue #251 (October 1982).
Contrary to numerous sources, Blackhawk is never referred to as either Polish or Polish-American.
The letters page of Blackhawk (DC, 1957 series) #256 (March 1983) places Mark Evanier's version of the Blackhawks on Earth-One.
Refer also to [Blackhawk [Bart Hawk]][5429] and [Blackhawk [Janos Prohaska]][31114].
[5429]: https://www.comics.org/character/5429/
[31114]: https://www.comics.org/character/31114/