As I understand it, the expression "mother of all [fill in the blank]" is an common bit of Middle Eastern hyperbole that dates back centuries, but the earliest I can remember hearing it was when Saddam Hussein warned that the "mother of all battles" awaited the U.S. military in the First Gulf War in 1991. (Spoiler alert: he lost.) 

At the time Saddam was widely mocked for using such an over-the-top expression, but I guess now that despotism is all the rage, braggadocio is okay. It reminds me of when my son went through a WWE phase a few years ago. The wrestler who could boast about himself the loudest and deliver the biggest (fake) pummeling to his opponent was the one all the kids thought was the coolest.

In a human being that's an obvious sign of insecurity and immaturity. But when it happens in a nation's military? Well, if we weren't talking about a weapon of mass destruction, I'd say it was funny. As it is, it's just profoundly sad.