Who was the US targeting and why?

Coalition officials said they deployed the most powerful weapon in the the United States' non-nuclear arsenal to finish a fight against Daesh fighters holed up in mountainous caves in eastern Afghanistan, a Pentagon statement said Thursday.

Afghanistan's Defence Ministry today said that "no civilian has been hurt and only the base, which Daesh used to launch attacks in other parts of the province, was destroyed," adding that 82 Daesh-affiliated militants were thought to have been killed.

Local reports have so far suggested that the Achin district in Afghanistan's eastern Nangarhar province had been infiltrated by militants who have pledged loyalty to Daesh. Ongoing fighting in the area had killed one American soldier last week.

Nangarhar province, whose main economic sector is agriculture, is home to Jalalabad, Afghanistan's second-largest city. The last census Afghan census, in 2006 counted the population at about 95,000 people, mostly Pashto speakers.

Nangarhar's Achin disctrict was once one of the country's largest producers of tobacco and poppy – which can be used to produce the lucrative drug opium.

What are Afghans saying?

The former president of Afghanistan, Hamid Karzai, "vehemently" denounced the bombing by the US military, taking to Twitter to say: "This is not the war on terror but the inhuman and most brutal misuse of our country as testing ground for new and dangerous weapons."

There was concern that civilians may have also been killed in the strike.

Some called the strike "counterproductive" and could likely inspire more militants to join the fight against US forces, who face a protracted and unpopular battle in Afghanistan.

Lingering frustrations at the Afghan government's ineffectiveness at stopping the violence in the country came to the surface.

Was the "mother of all bombs" necessary?

Thursday's strike was the first time the GB-43 was used in a combat operation. It cost over $300 million to develop, and a single payload costs an estimated $16,000,000 USD.

The bomb weighs close to 10,000 kilogrammes and is so big that it rolls out of the rear of a plane with the help of a parachute. It is specially designed to destroy caves, tunnels and other underground facilities used by militants.

Militants targeted in the Achin district were hiding out in a remote and mountainous terrain that is heavily permeated by underground tunnels, making them inaccessible to Afghan and US forces.

Before the missile was launched, the Afghan forces on the ground met fierce resistance from Daesh who were firing from six mountainside tunnels. The military then retreated and called for coalition air support, an American official told The New York Times.

"The ground forces could not do it, so the Americans bombed the area," General Dawlat Waziri, spokesperson for the Afghan Ministry of Defence told reporters Friday.

The use of IEDs, bunkers and tunnels made fighting the militants difficult, and necessitated "right munition to reduce these obstacles and maintain the momentum of our offensive," the commander of US forces in Afghanistan, General John Nicholson said in a statement following the strike.

How does Daesh threaten Afghanistan?

Notorious for their brutal reign of terror in Syria and Iraq, Daesh has been making inroads into Afghanistan in recent years. Fighters from the Pakistani and Afghan Taliban, as well fighters from around the Central Asian region disaffected by the Taliban's waning power declared a Daesh offshoot franchise in Afghanistan and Pakistan.

Calling itself "the Islamic State in Khorasan Province" (ISKP), they been active in Afghanistan since January 2015, roughly six months after the groups led by Abu Bakr al Baghdadi declared a "caliphate" and began sweeping up territory throughout Iraq and Syria. They claimed responsibility for a suicide attack that killed 80 people and injured hundreds in July 2016, and an attack in March 2017 when gunmen dressed as doctors attacked a hospital in Kabul, killing 38 people.

Afghanistan has been at war for nearly 16 years. The government is plagued with difficulty fighting a battle for legitimacy on multiple fronts, against the Taliban, Daesh, poverty, and an ineffective and often corrupt government.

Within a short span of time they expanded in five provinces of Helmand, Zabul, Farah, Logar and Nangarhar but group is most active in eastern parts of Afghanistan. Though the militant branch in Afghanistan claims loyalty to Daesh, whose main centre is in Iraq and Syria, the connection is believed to little more than opportunistic branding. Many of the fighters who joined ISKP were trained in Pakistan by the Taliban, who have now become their rivals in terror.

Coalition forces believe that the Daesh fighters often switch allegiances between armed groups, making it difficult for them to operate. Afghan authorities estimated in late 2015 that over 2,000 militants had taken root in Nangarhar province, many of them taking their families with them.

Nicholson said US forces had taken "every precaution to avoid civilian casualties", but did not provide further details.

The site was closed off Friday, and local reporters were waiting to be granted access to the area by the authorities.

While some Afghan provincial officials have sought to garner the world's attention by playing up the Daesh threat in the face of dwindling foreign aid and a receding international troop presence, the group has been steadily losing ground.

It has depleted to about 700 fighters from 3,000 in early 2016, NATO says, noting that coalition operations have killed 12 of Daesh's top-ranking commanders in Afghanistan last year. The US military estimates that there are between 600 and 800 Daesh fighters in the country mostly based in southern Nangarhar province, including Achin. But Afghan forces believe the militants could number could be up to 1,500.

Reporting by Mehnaz Yaseen and Shawn Carrié