The swift Taliban victory in Afghanistan could have a profound impact on its Central Asian neighbours, the Middle East and Africa where governments are battling radical fundamentalists.
During its campaign, the Taliban were reinforced by jihadis from several countries and groups as well as locally-based fighters from longstanding partners al-Qaeda and Islamic State, also known as Isis.
The Taliban’s triumph is likely to have boosted morale and determination to carry on with the jihadi mission to conquer fresh lands and impose strict religious practices and laws.
Ahead of the Taliban's sweep into Kabul, former US defence secretary Leon Panetta told US National Public Radio, "The Taliban are terrorists, and they're going to support terrorists." He said they "will provide a safe haven for al-Qaeda, for Isis and for terrorism in general".
While Panetta focused on the national security threat posed to the US, this is far more imminent and potent for countries with downtrodden, disaffected Muslim populations.
Fostered, trained and armed by Pakistan's Inter-Services Intelligence, the Taliban first conquered Afghanistan in 1996 but were ousted from power by the US in 2001 following the attacks on New York and Washington by Taliban-hosted al-Qaeda.
Since then, Afghan Taliban leaders have based themselves in the Pakistani city of Quetta, from where they prepared for Sunday's return to Kabul.
Pakistan could face blowback for sponsoring and hosting the Afghan Taliban if the Pakistani Taliban revive. This movement is infamous for the 2012 shooting of schoolgirl Malala Yousafzai and the 2014 Peshawar school massacre which killed more than 140 people and prompted Pakistani security to crack down hard on the movement.
Pakistani Taliban and other foreign jihadis have always been a Taliban asset. To maintain their dominance and secure Afghanistan’s borders, the Taliban, which the US estimates has only 85,000 fighters, may, for the short-term, depend on non-Afghan jihadis for back-up.
For example, Tajik Taliban recently assumed control of traffic on the Afghan side of a strategic border crossing with their country.
Central Asian countries differ over the Taliban's victory. In anticipation, Turkmenistan negotiated cross-border development projects with Taliban officials, but Tajikistan and Uzbekistan – which harbour active and ambitious Taliban-type movements determined to follow the Taliban's example – are wary of its success.
They reportedly fear both an influx of Afghan refugees and the migration to Afghanistan of northern Central Asian jihadis who could train and arm to take over their homelands. The Taliban-inspired Islamic Movement of Uzbekistan not only seeks to overthrow the country's secular government but also to create a pan-Central Asian Islamic caliphate.
Since the Taliban refused to honour the agreement with the Trump administration to halt al-Qaeda and Islamic State activities in Taliban-held territory in exchange for full US troop withdrawal, the movement cannot be expected to rein in its allies.
Instead, the Taliban could accord them freedom train and export fighters to the battlefields of Iraq, Syria, Yemen, and Libya in the Arab world and Niger, Chad, Mali, Burkina Faso and Mauritania in Africa's embattled Sahel region, as well as elsewhere in the continent.