Yesterday, when the Taliban spokesman Zabihullah Mujahid said that his fighters killed more than 100 soldiers in a complex suicide assault at the Afghan National Army’s 209th Shaheen Corps Headquarters near the provincial capital of Mazar-i-Sharif, his claim was dismissed as routine inflation of battlefield casualties.

Today, Zabihullah’s boast has become reality, possibly making it the most deadly Taliban attack on a military installation in nearly five years.

Afghan officials are reporting that more than 140 Afghan soldiers are believed to have been killed, and that number may rise. From Reuters:

One official in the northern city of Mazar-i-Sharif, where the attack occurred, said on Saturday at least 140 soldiers were killed and many others wounded. Other officials said the toll was likely to be even higher. They spoke on the condition of anonymity because the government has yet to release exact casualty figures. The defense ministry said more than 100 soldiers were killed or wounded.

The suicide assault was carried out by 10 Taliban fighters dressed as Afghan policemen, according to Reuters. According to the Taliban, four of them were Afghan security personnel who had “infiltrated” the ranks. Mujahid also posted a photograph he claimed was the assault team (see above).

In a statement released today by Taliban spokesman Mujahid that was translated by the SITE Intelligence Group, he claimed that “among these mujahideen, four of them were soldiers who infiltrated the enemy ranks, where they served as soldiers inside the Shaheen Corps headquarters for a long time, waiting for the zero hour.”

Yesterday’s raid may have been one of the most effective Taliban attacks on a military installation in Afghanistan since Sept. 2012, when a team of fighters penetrated security at Camp Bastion in Helmand province and destroyed six USMC Harriers and damaged two others, and killed two US marines, including the Harrier squadron commander.

After the Camp Bastion attack, the US military said the Taliban team “appeared to be well equipped, trained and rehearsed.” The same could likely be said the attack on the Afghan National Army’s 209 Shaheen Corps Headquarters, given the decimation.

Bill Roggio is a Senior Fellow at the Foundation for Defense of Democracies and the Editor of FDD's Long War Journal.

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