They are supposed to have rigorous, thorough training about what types of channels are considered secure and legal, and which types of communications are secret, top secret, confidential, etc.
Discussing war plans is top secret and if the highest ranking members of our military don't understand that, we are all fucked. The thing is, they do know that, but they are obviously choosing to communicate on Signal so that all of their communications are off the record and undiscoverable, which is another primary reason that what they are doing is illegal and immoral.
Oh, shut the hell up. You damn well that kidnapping college students off the streets to send them to prison labor camps is SEVERAL STEPS beyond anything that happened in the past.
For real, fuck off. Do something productive. Be better.
And also, be less of a pathetic liar. Obama did not invent the phrase "enemy combatant". I was there when GWB used it every damn day.