(CNN) In an interview with C-SPAN about the Vietnam War that ran over the weekend, Sen. John McCain said this:

"One aspect of the conflict, by the way, that I will never, ever countenance is that we drafted the lowest income level of America, and the highest income level found a doctor that would say they had a bone spur. That is wrong. That is wrong. If we are going to ask every American to serve, every American should serve."

While McCain didn't mention any names, anyone paying any sort of attention knows that he is talking about President Donald Trump, who received five deferments during the Vietnam War, including one for -- you guessed it! -- bone spurs.

Trump, despite being in generally good health at the time, received a diagnosis of bone spurs, which gave him a draft status that kept him out of the war. In an interview with The New York Times about the deferment , Trump was unable to remember the name of the doctor who had diagnosed him but noted: "I had a doctor that gave me a letter -- a very strong letter on the heels." He added that the problem was "temporary" and "minor." (Trump received four further education deferments.)

The "bone spur" shot is McCain's latest jab at Trump in a decidedly tempestuous relationship that dates back to at least 2015.