On Thursday, Trump gave a shout-out to the late Gen. John J. Pershing on Twitter, reigniting the public's interest in the American military figure. During his service, Pershing got the nickname "Black Jack," and while that's an unassailably cool nickname, it wasn't originally intended as a compliment.
Pershing is most famous nowadays as the subject of a debunked urban legend which claims that he dipped bullets in pig's blood while fighting Muslim enemies in the Philippines. But Pershing had a long career in the U.S. military, commanding U.S. forces in Cuba, the Philippines, and Europe. He's the first and only active-duty officer to become General of the Armies, the highest-ranking position in the U.S. armed forces.
In 1897, Pershing became a tactical officer at West Point, and that's where he was given the nickname "Black Jack." There are two different (but not mutually exclusive) stories about how he got that name. According to one tale, Pershing was called "Black Jack" because he commanded black troops during the American-Indian Wars of the late 19th century. It's also alleged that he was given the nickname due to the harsh, unforgiving manner of discipline he exerted during his time as a West Point instructor.
The first story makes sense. Pershing's first name is "John," for which "Jack" is a nickname, and he was a white man who commanded black troops. Hence "Black Jack." The second story is more confusing, though. What does the nickname have to do with being a harsh disciplinarian? The phrase "black jack" can be used to refer to a card game or a weapon, but nothing about it alludes to an instructor who rules with an iron fist.
Although the answer isn't entirely clear, now is probably a good time to mention that Pershing was initially given a much more reprehensible nickname: "N-----r Jack." That one didn't stick, and it quickly gave way to "Black Jack." But if Pershing was indeed disliked by his cadets as much as historians believe, and if those cadets did indeed him that nickname in response, that would strongly suggest that Pershing's nickname was intended primarily as a racist insult — an attempt to highlight his perceived negative traits by likening him to a black person and referencing his time commanding black troops.
In any event, Trump was harshly criticized by Democrats and Republicans alike for giving new life to the discredited pig's blood myth, endorsing religious bigotry in the U.S. military, and mischaracterizing the service of a celebrated American general. Right-wing blogger Jennifer Rubin wrote on Twitter that, in light of Trump's Pershing comment, she's giving new consideration to the argument that Congress should remove Trump from office by invoking the 25th Amendment.