COLORADO SPRINGS, Colo. — The U.S. military will further harden U.S. bases against the Islamic State and other terrorist groups, Defense Secretary Ash Carter said Friday, as part of a $180 million spending effort over the next three years to better protect troops from attacks.

The announcement follows attacks and increased threats against U.S. troops by individuals inspired by Islamic extremist ideology or overseas groups. In 2014, a law enforcement bulletin obtained by Fox News warned of an increased threat of “lone wolf” attacks from ISIS sympathizers. Last July, one such lone wolf opened fire at a military recruiting center in Chattanooga, Tennessee, killing four Marines.

“As we learned from the tragedy in Chattanooga last summer, ISIL has demonstrated a clear intent to target U.S. service members and facilities, or at least to inspire others to do so. Providing greater force protection for men and women serving today is one way we honor those service members who lost their lives last August,” Carter said, at the headquarters for U.S. Northern Command, or NORTHCOM, and the North American Aerospace Defense Command, or NORAD.

The funds will go to reinforce doors, improve exits and procedures, install better alarms and access controls, and set up an “early warning” system to pass the word about threats and incidents to all military personnel within 20 miles of a military facility inside of 10 minutes.

Currently, the military issues a lockdown alert in the event of an active shooter, but that alert is limited to one facility.

“That’s a direct response to Chattanooga, where the killer targeted two facilities 11 miles apart in a span of 12 minutes,” said Carter.

Carter today highlighted last August’s strike that killed Junaid Hussain, the ISIS figure who released the personal details of more than 1,000 U.S. military members and “who sought to inspire wannabe jihadists to conduct attacks against us in DOD.” Carter described Hussain as “central figure in recruiting ISIL sympathizers to carry out lone-wolf attacks in the West,” said Carter.