It's still unclear exactly what motivated the suspected gunman behind the July 16 shootings in Chattanooga, Tennessee.
But one thing is clear: U.S. military facilities both at home and abroad are prime targets for would-be jihadists.
On July 22, Italian police reportedly arrested two men who planned to attack an Italian airbase where U.S. airmen safeguard nuclear weapons.
Just a day earlier, British prosecutors charged a man arrested July 14 for planning to attack U.S. troops in the United Kingdom. Authorities did not identify specific locations. It is unclear whether it was that specific threat that prompted the 48th Fighter Wing to cancel this year's July 4 celebrations at Royal Air Force Feltwell.
Those two incidents are part of a long and growing list of thwarted attacks against U.S. military facilities. An August 2014 edition of al-Qaida in the Arabian Peninsula's magazine "Inspire" published an article about how to make bombs that suggested jihadists target the Air Force Academy in Colorado.
And this past March, Hasan Edmonds, a specialist in the Illinois Army National Guard, and his cousin Jonas were arrested in March on suspicion of planning to attack the Joliet Armory in that state.
Other entries on the list include:
- In February, an Ohio man who was originally from Somalia was arrested in Columbus for allegedly planning to attack a U.S. military base in Texas. He had previously traveled to Syria to fight with Jabhat al-Nusrah, an al-Qaida affiliate.
- A man who emigrated from Uzbekistan to Idaho was arrested in May 2013 after allegedly telling an FBI informant that he wanted to use a bomb to attack an unnamed U.S. military base.
- In 2012, three men received prison sentences ranging from 15 to 45 years for allegedly planning to Marine Corps Base Quantico in Virginia. They were among eight men arrested on suspicion of raising money and stockpiling weapons for terrorist attacks.
- Five men were convicted in 2008 of planning to attack Fort Dix, New Jersey. Four of the men were later sentenced to life and in prison, while the fifth received a 33-year sentence. The U.S. attorney who announced their arrests in 2007 was none other than Chris Christie, who later became governor of New Jersey and is now vying for the Republican nomination in the 2016 presidential election.