Tom Vanden Brook

USA TODAY

KABUL — Defense Secretary Jim Mattis on Monday said the United States and NATO will have to confront Russia over its support for the Taliban, remarks that came days after a massacre of Afghan troops inside a mosque and amid a review of the American strategy here.

Mattis was in the Afghan capital days after the insurgent attack on an Afghan army base killed more than 140 soldiers and wounded dozens more. The slaughter prompted the resignation Monday of top Afghan defense officials.

Mattis’ Afghan visit, which included meetings with Afghan President Ashraf Ghani and Australian Prime Minister Malcolm Turnbull, was the last leg of a tour of the Middle East and Africa. Mattis also met Monday with Army Gen. John Nicholson, the top U.S. and NATO commander, who told the Senate earlier this year that he needs thousands more troops to advise Afghan forces. There are about 8,400 American troops here now.

The Taliban have been receiving an increasing flow of arms, including machine guns, and funding from Russia, according to senior U.S. military official who was not authorized to speak publicly. Nicholson acknowledged receiving continuing reports of Russian assistance to the Taliban.

“We’re going to have to confront Russia,” Mattis said, adding supplying the Taliban with weaponry would be a violation of international law.

U.S. troops are also waging a counter-terrorism war against Islamic State militants and al-Qaeda terror affiliates. Earlier this month, Nicholson attacked ISIS insurgents with one of the largest conventional munitions in the U.S. arsenal, the Massive Ordnance Air Blast, or MOAB, also referred to as the Mother of All Bombs.

Since early March, the U.S.-led coalition has killed 538 Islamic State fighters. The strikes have reduced ISIS strength from about 3,000 militants in 2015 to about 800 today, according to the military official.

But it is the Haqqani network, an extremist group affiliated with the Taliban, that is likely responsible for the attack at the army base last week. Ten attackers committed the strike on the Afghan army post.

The attackers appear to have used the ruse that they were bringing a wounded Afghan solider to the base for treatment. That allowed them to pass through three checkpoints, the Defense official said.

They also seem to have had inside information on the best time to carry out the massacre: during prayers when most of the Afghan troops were not carrying weapons. Suicide bombers killed some of the soldiers, while others were cut down by small arms fire and grenades.

Mattis: Taliban 'not devout'

The attack on Afghans during worship shows the depravity of the Taliban, Mattis said.

“They have no religious foundation,” he said. “They are not devout anything.”

There has been progress in the counter-terrorism fight, Nicholson and the official said.

Nicholson’s request for more troops is a reversal from the last years of the Obama administration, which had sought to end the American war here that began after the terror attacks of Sept. 11, 2001.

But a resurgent Taliban, and the presence of a number of terror groups with designs in U.S. and western targets, convinced Obama to stop the withdrawal. Mattis and President Trump will now decide if an escalation is in order.

Mattis said he would need time to reach a decision on U.S. troop levels in Afghanistan.

The new administration is inheriting what the Defense official described stalemate between the Afghan government and the Taliban, the Islamic fundamentalist movement that governed Afghanistan until it was toppled in October 2001, shortly after the U.S. invasion. The Taliban had sheltered Osama bin Laden, the al-Qaeda leader who coordinated the 9/11 attacks.

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