U.S. Secretary of Defense Jim Mattis is capping off his trip to Africa and the Middle East with an unannounced visit to Afghanistan.
His trip comes days after a Taliban attack on an Afghan military base killed at least 140 soldiers in the northern part of the country.
Two of Afghanistan's top military officials resigned as a result: Defense Minister Abdullah Habibi and Army Chief of Staff Qadam Shah Shahim.
While there, Mattis met with U.S. Army Gen. John Nicholson. He's the U.S. commander who authorized the use of the country's largest non-nuclear bomb to target an ISIS tunnel system earlier this month.
Nicholson's also urged Congress to send more U.S. troops to Afghanistan, where it's held a military presence since 2001.
During his last year in office, former President Barack Obama oversaw a withdrawal of 1,400 troops from Afghanistan. There are currently 8,400 U.S. troops stationed there.
But a recent report to Congress said Taliban insurgents have taken control of more territory while the number of Afghan national security forces are decreasing.
Mattis also met with Afghanistan's president, Ashraf Ghani, on Monday.