Alert level for US bases in Europe raised due to Russian threat

American defense officials raised the security alert level at military bases in Europe over the weekend in response to vague threats from the Kremlin that Ukraine could deploy long-range weapons on Russian territory, according to American and Western officials.

Officials said there was no concrete intelligence on possible Russian attacks on American bases. Any such attack by Russia, whether overt or covert, would be a significant escalation of the war in Ukraine.

Russia has stepped up its sabotage operations in Europe to disrupt the flow of supplies to Ukraine. So far, no American bases have been targeted in these attacks, but U.S. officials said raising the alert level would help keep soldiers on guard.

Throughout the war, US officials assumed that President Vladimir Putin was unwilling to expand the war beyond Ukraine’s borders.

But the increased American and European aid – and the loosening of restrictions on the use of these weapons – has caused consternation in Moscow, American officials said. Recent Russian comments have made some American and European officials suspicious.

Ukraine is using American longer-range missiles, known as ATACMS, to penetrate deep into occupied Crimea. The United States has also said Ukraine could use these missiles to launch cross-border attacks on Russian military targets.

The attacks on Crimea prompted Russia to summon US Ambassador Lynne M. Tracy to the State Department. And on June 24, a Kremlin spokesman said that any direct US involvement in the war that had led to the deaths of Russians “must have consequences.”

The US decision to supply longer-range weapons and ease restrictions on their use followed Britain’s decision to supply Storm Shadow cruise missiles to Ukraine, which Kyiv had used to attack military targets in Crimea.

The attacks with Western weapons, especially in Crimea, proved effective: they damaged the Russian army’s logistics centers and further weakened the Russian Black Sea Fleet.

But the success of the attacks has prompted Moscow to look for ways to deter further attacks.

In recent months, Russia has stepped up a series of sabotage attacks in various locations in Europe. The campaign, carried out by Russian military intelligence, has at times appeared heavy-handed, including a fire at an Ikea store. But NATO has repeatedly warned against such incidents, and Britain expelled the Russian defense attaché after a fire at a London warehouse.

Military bases that provide training, intelligence and other support to Ukraine could be a logical next target, although there is no concrete intelligence to suggest that Russia is considering such an attack.

Protecting military bases and the people who live and work there falls under what the Pentagon commonly refers to as force protection. Beyond things like simple fencing or guards at base gates, this protection includes a range of increasingly restrictive security measures that can be implemented depending on the given threat.

Most U.S. military installations around the world are in the second-lowest level of such protection, known as “Alpha,” which includes measures such as ordering officials to test their communications equipment and increased random checks of vehicles and people entering the bases.

At the other end of the spectrum is the “Delta” state, which is triggered when an attack is imminent or already underway. At this level, non-essential functions such as schools on the base are shut down, all vehicles are searched at the entry gates, more guards are placed, and the movement of almost everyone on the base is severely restricted.

Currently, American military bases in Europe are at Charlie status, the second highest level and the highest level of readiness that can reasonably be maintained over an extended period of time.

Over the weekend, Commander Daniel Day, a spokesman for the US European Command, said the military was urging its soldiers to “always remain vigilant and alert.”

In a statement on Monday, the European Command said its officials would not elaborate on the measures they are taking to protect their operational security.

“Our heightened vigilance is not due to a single threat,” the command’s statement said, “but is a result of excessive caution in the face of a combination of factors that potentially affect the safety of U.S. soldiers in the European theater.”

Eric Schmitt contributed to the reporting.