At any given time the United States has an aircraft carrier deployed somewhere around the world, usually in a hot spot such as the Persian Gulf or the Western Pacific.

But for the first week of this year, for the first time since World War II, no U.S. aircraft carriers were deployed, anywhere, a Navy spokesman confirmed.

The USS Dwight D. Eisenhower had been in the Persian Gulf, contributing airpower to the counter-Islamic State campaign in Iraq and Syria. But it returned to its homeport of Norfolk, Va., on Dec. 30, after a seven-month deployment. And none of the Navy's nine other aircraft carriers was on deployment.

Which is why it appears Pentagon spokesman Peter Cook took the unusual step Thursday of announcing the "routine" deployment of the USS Carl Vinson to the Western Pacific.

The San Diego-based carrier strike group along with its escort ships "will conduct bilateral exercises in the Indo-Asia-Pacific region, to include anti-submarine warfare, maneuvering drills, gunnery exercises, and visit board, search and seizure subject-matter expert exchanges," according to Cook.

The unusual gap in carrier presence is due in part to longer-than-expected maintenance for the USS George H.W. Bush, which was supposed to take eight months, but ended up taking 13 months. The Navy blamed the delay on increased wear and tear that resulted from an extended deployment. If it had left when it was supposed to, it would have relieved the Eisenhower in the Gulf.

It's now expected to leave Norfolk for the Persian Gulf sometime this month, ending a two-month gap in the Middle East. That sort of gap has happened before.

"We have significant capabilities within the U.S. military," said Cook, downplaying the significance of the carrier gap. "They are not all limited to aircraft carriers and so those deployments are determined based on, again, operational needs, operational requirements and we make adjustments accordingly."

Cook said the absence of a carrier in the Gulf or the Pacific does not mean the U.S. is vulnerable.

"We have had a significant presence in both those areas and will continue to have a significant presence even though we may not at any one particular time have an aircraft carrier there," Cook said.

And the Navy isn't completely without flattops at sea. The USS Makin Island, an amphibious assault ship, is on deployment in the Middle East. The ship is smaller than an aircraft carrier and deploys with Marines, landing craft and helicopters.