One of the most powerful weapons in the US Navy’s arsenal made a rare port call in Guam over the weekend, sending a message to allies and foes amid increasing tensions in the Indo-Pacific, analysts said.

The USS Nevada, an Ohio-class nuclear-powered submarine carrying 20 Trident ballistic missiles and dozens of nuclear warheads, pulled into the Navy base in the US Pacific Island territory on Saturday.

It’s the first visit of a ballistic missile submarine — sometimes called a “boomer” — to Guam since 2016 and only the second announced visit since the 1980s.

“The port visit strengthens cooperation between the United States and allies in the region, demonstrating US capability, flexibility, readiness, and continuing commitment to Indo-Pacific regional security and stability,” a US Navy statement said.

The Navy says Ohio-class submarines stay an average of 77 days at sea before spending about a month in port for maintenance and replenishment.

It’s rare for one to even be photographed outside their home ports of Bangor, Washington, and Kings Bay, Georgia. The secrecy surrounding the ballistic missile submarines makes them the “most important survivable leg of the nuclear triad,”.