The US has defended the use of the largest non-nuclear bomb ever used in combat, saying the decision was based on tactical considerations.

The MOAB – ‘mother of all bombs’ – is claimed by the US military to have killed 36 Isis supporters.

Army Gen John W Nicholson, commander of US forces in Afghanistan, said in a written statement: "This is the right munition to ... maintain the momentum of our offensive."

Pentagon officials said also said Gen Nicholson didn't need and didn't request President Donald Trump's approval before using MOAB.

Details about the raid came as video footage emerged of the moment the 21,000lb warhead was dropped.

It was the first time the MOAB weapon was used in combat operations.

It is the military’s largest non-nuclear weapon and was used to strike the Achin area in the Nangarhar province on the border with Pakistan.

The blast could reportedly be seen nearly 20 miles away, but the blast radius is approximately one mile.

According to Reuters, Afghan President Ashraf Ghani's office said in a statement that the strike was part of a joint operation between Afghan and international troops.

Retired US General Mark Hertling told the broadcaster the “Air Force must have had a good target...normally smaller artillery could have been used”.

It has been confirmed that Donald Trump did not give an explicit order to drop the bomb in the Achin district of Nangarhar. It was US command in Afghanistan and Gen. Nicholson who made the decision.

A Pentagon spokesperson also told The Independent that the strike was required to be authorised by US Central Command leader General Joseph Votel due to the fact that the bomb had to moved through different theatres of war.

Mr Trump earlier said he had given “my military...total authorisation".

A Pentagon spokesperson told The Independent that Mr Nicholson “received authorities” in January 2017. But, it has not been made clear whether that came from an outgoing President Obama or the new Trump administration

Supporters of Mr Trump have said this ‘carte blanche’ authorisation for the US military is a new approach to using military power.

President Obama was seen by his critics, like former President Reagan’s National Security Adviser General Oliver North, as “micromanaging” US generals.

Mr Trump also mentioned his new approach compared to the previous Obama administration in his comments. He said there is a “tremendous difference” between “the last eight weeks and [compared] to really what's happened over the last eight years.”

However, Mr Obama was no ‘dove’ when it came to military operations, making extensive use of drones to drop missiles in areas of conflict including Iraq and Syria.

White House Press Secretary Sean Spicer said the MOAB was used to target tunnels and caves Isis fighters used to “move around freely”.

He referred to the GBU-43 MOAB has a “large, powerful and accurately-delivered weapon”.

The MOAB was actually developed using the parts of existing bombs by the US Air Force back in 2002 and “what it does is basically suck out all of the oxygen and lights the air on fire,” said Bill Roggio of the Foundation for Defence of Democracies think tank, to the Air Force Times.

Tested in 2003 at a base in Florida, the MOAB was moved to Iraq in the early years of the war there, however it was never deployed. The bomb is so large that it is dropped by a parachute from a cargo plane, the C-130 Hercules.

The Pentagon said the plane used in this particular mission was already located in Afghanistan ahead of the strike.

PJ Crowley, the assistant secretary of state in the Obama administration, said the purpose of the bomb was to create “a minor earthquake” that would collapse tunnels and caves and cause shockwaves in the immediate area.

Though Mr Crowley said the MOAB would have a “profound effect” what impact it will have on operations of IS Khorosan remains to be seen.

The Isis fighters in the area say they are affiliates of the larger Isis terror group, referring to themselves as IS Khorosan - which is the historical name for a region that includes parts of Afghanistan, Turkmenistan, Tajikistan, and Uzbekistan.

A source told The Independent that affiliations of such terror groups in the area do change periodically.

Mr Nicholson said in a statement that this particular group has been using bunkers, tunnels, and improvised explosive devices to defend themselves.

The Trump administration has also been sending signals in the Pacific to a nuclear-armed North Korea recently.

Mr Trump said the use of the MOAB was not necessarily done to send a message to North Korea, but that “It doesn’t make any difference if it does or not — North Korea is a problem, the problem will be taken care of".