In a rare concurrence of events, a carrier strike group and all three ships of a Navy Amphibious Ready Group (ARG) are in the Persian Gulf, for a total of nine U.S. Navy ships in region, defense officials told USNI News on Tuesday.

USS Bataan (LHD-5), embarked with about 1,000 Marines from the 22nd Marine Expeditionary Unit (MEU), transited the Strait of Hormuz on Monday joining ships of the George H.W. Bush carrier strike group (CSG).

The two other ships in the Bataan ARG — USS Gunston Hall (LSD-44) and USS Mesa Verde(LPD-19) — entered the region earlier this month.

Some ships in gulf are part of a presence mission in reaction to the Iraq and Syria Islamic State (ISIS or ISIL) insurgency and some are in the gulf for earlier scheduled operations, a navy official told USNI News.

Gunston Hall is currently in port in Kuwait, while Bataan was due in the region earlier but was delayed in the Mediterranean.

Bataan had been stationed off the coast of Libya in late May, following rising violence in a post- Moammar Gadhafi Libya and an assault on the prime minister.

Mesa Verde, a San Antonio-class amphibious warship, entered the gulf in mid-June following several ISIS attacks along with elements of the Bush CSG.

ARG/MEUs typically deploy together but often individual ships break off for so-called disaggregated operations.

USS George H.W. Bush (CVN-77) is accompanied by one cruiser and five destroyers —guided missile cruiser USS Philippine Sea (CG-58) and the guided-missile destroyers USSTruxtun (DDG-103), USS Roosevelt (DDG-80), USS O’Kane (DDG-77) and USS Arleigh Burke (DDG-51).

Though not all of the ships are part of the presence mission that is focused in Iraq, all of the ships can respond to military threats if required, the navy official said.