Transcript for Impact of 'mother of all bombs' strike in Afghanistan

Let's talk about the moab more, the most powerful conventional bomb in the U.S. Force. It has a blast radius of one mile. Its mushroom cloud can be seen by 20 miles away. Each one costs $16 million and so far the U.S. Has made 20 of them. Let's talk about it with Steve ganyard who served in the Pentagon and Marine Corps as a fighter pilot. This was developed ten years ago. Why use it now? It's the first time they've had the opportunity where they had ISIS fighters isolated from the battlefield so the rules of engagement have not changed under president trump. The U.S. Military still goes to great lengths not to hurt civilians so this is the first time they had it isolated where the blast would not affect -- It goes across the surface. Here we have these fighters down in this deep valley, this is really rugged terrain so the blast was focused and pushed up into the caves to take out these fighters. If U.S. Fighters would have had to fight uphill and dig them out of the cave it would be dangerous so you could say they saved American lives. How do we find out the total impact here? The Afghan government is saying it killed about 36 ISIS fighters. General Nicholson in kabul a few minutes ago said the U.S. Has troops on the ground at the site right now so they'll go in and look for intelligence, they'll look for computer hard drives and things like that to see if they can figure out why and how they've been operating in the area. They fear of blowback? As you said it saves American lives by taking out ISIS militants. The message we have to strike back now? It sends a message to ISIS but the real question as we watched as Martha said we watch North Korea here, was that heard on the other side of the world in Pyongyang and will it make an impression on Kim Jong-un? The answer? I think so. And finally here one of the things we're seeing as Terry said a more muscular approach from president trump, he is giving military commanders on the ground a lot of leeway. He is. Well, the decision-making process has been devolved down so president Obama controlled that tightly at high levels. What we're see is tactical commanders can make decisions on the ground in Iraq and Afghanistan.

This transcript has been automatically generated and may not be 100% accurate.