American military forces in Europe are raising their threat level for unclear reasons, but the level to which it has been raised suggests commanders are fearing a potential terrorist attack. 

On Sunday, the threat level was raised to “Charlie” by European Command, though no explanation was given, according to the military-focused news outlet Stars and Stripes. The last time the threat level was raised on the continent was in 2021 as Russia was amassing forces on the border of Ukraine before its invasion. 

The “Charlie” threat level is the second-highest alert the American military offers for its servicemembers and staff. Only Force Protection Condition Delta, which is instituted only after an attack has taken place, is more serious. 

The “Charlie” status “applies when an incident occurs or intelligence is received indicating some form of terrorist action or targeting against personnel or facilities is likely,” according to the Army. 

The heightened security alert came from the European Commander headquarters at Stuttgart, Germany, and it warned all staff that the status would be in place until further notice.

The force protection condition was raised across the country, including at Rheinland-Pfalz and Ramstein Air Base, which include installations in Romania and Bulgaria. The Spangdahlem air base in western Germany instructed its servicemembers to not wear their uniforms off-base as a safety measure. 

Aviano Air Base in Italy also raised its threat level to “Charlie.”

The Stuttgart garrison told Stars and Stripes that some services on their base would not be available to servicemembers and staff during the heightened state of security, including barbershops and some cafeterias.

“Many other services will have significant numbers of employees teleworking or offices will be opened with reduced staff. Customers should maintain flexibility and allow for longer-than-normal service times,” the Army said.