US Defense Secretary James Mattis has arrived in Afghanistan on a surprise visit aimed at shaping President Donald Trump’s strategy in the conflict-ridden country, amid signs of renewed violence.

Mattis arrived in the capital city of Kabul on Monday and was expected to meet with Afghan officials as well as American military troops stationed there.

The Pentagon chief’s arrival coincided with the resignation of his Afghan counterpart Abdullah Habibi and Army Chief of Staff Qadam Shah Shahim following a Taliban attack on a military base that killed some 140 soldiers last week.

The apparent security failure saw as many as 10 Taliban militants disguised as Afghan army personnel make their way into the base on military vehicles and gun down unsuspecting soldiers and new recruits. The final death toll is expected to be higher.

There are currently over 9,000 US troops in Afghanistan. Washington claims that the massive military presence is only aimed at maintaining security across the country until Afghan military forces are ready to take over the responsibility.

The Trump administration is reportedly planning to change the US mission’s stated priorities of training and advising Afghan forces and focus instead on carrying out strikes against terror groups such as Daesh (ISIL).

This change of policy was put on display earlier this month, when General John Nicholson, the top commander of US/NATO troops in Afghanistan, ordered his troops to drop the GBU-43/B Massive Ordnance Air Blast (MOAB) bomb—also known as Mother of All Bombs—on a purported Daesh target in the eastern province of Nangarhar.

Speaking to reporters in Israel last Thursday, Mattis defended using the 11-tonne munition and said he was not surprised by it.

“There was no surprise in terms of the effect of that battle at all. The battle was going on, and we were going to use what was necessary to break ISIS. And we’ve made that very clear in every theater where we’re up against ISIS,” the Pentagon chief said, using an alternative name for Daesh.

This is Mattis’ first trip to Afghanistan as defense secretary.