Just over a week after the U.S. dropped the so-called ‘Mother of All Bombs’ on ISIS fighters in eastern Afghanistan, a bloody attack on an Afghan army base has highlighted the country’s central security threat — the Taliban insurgency. The deployment of the 21,000 lbs GBU-43 bomb, the largest non-nuclear device ever used in combat, in Afghanistan’s Nangarhar province generated global headlines and was described by President Donald Trump as a “very successful mission.” But although ISIS has claimed several attacks in Afghanistan, including a raid on an Afghan army hospital in the capital Kabul in March that killed dozens of people, the April 21 raid on the army base in the northern city of Mazar-e-Sharif has underlined the worsening of the Taliban insurgency nearly two decades after the militants were ousted from the capital Kabul by a U.S.