US DROPS "MOTHER OF ALL BOMBS".

GEORGE STEPHANOPOULOS (ABC NEWS) (Off-camera) That is what we're seeing. Terry, thanks very much. Let's talk about the Moab more now, as Terry said, it's the most powerful bomb, conventional bomb in the US force. It has a blast radius of one mile. Its mushroom cloud can be seen from 20 miles away. Each one costs $16 million, and so far the US has made 20 of them. Let's talk about it now with our analyst Steve Ganyard who served in the Pentagon and the marine corps as a fighter pilot. So this was first developed about 10 years ago. Why use it now? [ABSTRACT FROM PUBLISHER]