U.S. Defense Secretary Jim Mattis signed orders to send additional troops to Afghanistan, the most concrete step yet by President Donald Trump’s administration in tackling America’s longest war, Reuters reported.

Mattis did not specify the size of the force, which will help combat Taliban insurgents and other armed Islamists.

“Yes, I have signed orders but it is not complete. In other words I have signed some of the (orders for) troops that will go and we are identifying the specific ones,” Mattis said.