The Associated Press says the Pentagon did a formal review of legal justification for the bomb's use when it was first developed.
The GBU-43, also known as the "mother of all bombs", is a GPS-guided munition and was first tested in March 2003.
The GBU-43 is about half the size of the smallest nuclear weapon ever built, the Davy Crockett nuclear artillery shell, retired in the late 1960's.
Just last Tuesday (Apr. 4), ISIS's spokesman, Abi al-Hassan al-Muhajer released the first statement on behalf of the terrorist group since Donald Trump took office, in which he said America is "being run by an idiot". It was not immediately clear how much damage the device did. But the Pentagon has come under increasing criticism that as it has intensified the fight against the Islamic State in Iraq and Syria, the civilian death toll has risen sharply.
Though no video has been released yet from Thursday's attack, the U.S. military has tested the bomb in 2008.
Donald Trump is the fifth consecutive USA president to serve as commander-in-chief while the US military is engaged in Iraq, and the fourth consecutive USA president to preside over military operations in Afghanistan.
The military is now gathering information on what damage the MOAB caused, but if the strike did indeed achieve its goal, this could have seriously damaged ISIS' presence in Afghanistan.
This may be the first deployment of the GBU-43 in USA military history, but based on Pentagon statements, it likely won't be the last.
The bombing in Afghanistan comes a week after Trump authorized a USA missile strike against a Syrian government air base - the first United States strike against the Syrian government in the country's six-year civil war.
The military said the bomb use in Afghanistan was dropped from a USA aircraft.
The MOAB was created to replace the BLU-82 "Daisy Cutter", which was used in Vietnam and in Afghanistan.
"North Korea is a problem, but the problem will be taken care of".
It's a change both Trump and Defense Secretary James Mattis wanted, the official said.
The top USA commander in Afghanistan said recently that he needed several thousand more global troops in order to break a stalemate in the long war with Taliban insurgents.
US officials say intelligence suggests Islamic State is based overwhelmingly in Nangarhar and neighboring Kunar province. US officials have said they believe the movement has only 700 fighters but Afghan officials estimate it has about 1,500.
"This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K", he added, using another name for the Islamic State in Afghanistan.