Marines assigned to the 26th Marine Expeditionary Unit embark the amphibious assault ship USS Kearsarge in Norfolk, in August. The Marines and sailors aboard were initially deployed to assist with Hurricane Harvey, but could instead help with Hurricane Irma relief. (Mass Communication Spec. 1st Class Deven B. King/U.S. Navy)

The U.S. military began preparing in earnest for Hurricane Irma on Wednesday, readying four Navy ships for potential disaster relief while moving aircraft and U.S. troops in advance of the arrival of the Category 5 storm.

Defense Secretary Jim Mattis has approved the use of the USS Oak Hill and the USS Kearsarge, amphibious ships now off Florida’s east coast, if help is requested from Gov. Rick Scott (R-Fla.), said Army Lt. Col. Jamie Davis, a Pentagon spokesman. The ships were originally deployed late last month with hundreds of Marines and sailors aboard to respond to Hurricane Harvey in Texas, but could instead be sent to Florida.

The Navy also is preparing to dispatch a second contingent of amphibious ships, the USS Iwo Jima and the USS New York, if they are needed. They have departed Naval Station Mayport in Jacksonville, Fla., to be loaded with disaster-relief equipment in Norfolk, said a Navy official, who spoke on the condition of anonymity to discuss ongoing operations. Maj. Brian Block, a Marine Corps spokesman, said that about 260 Marines will embark aboard the Iwo Jima.

The deployments come as the storm barrels west out of the Atlantic Ocean toward Florida. It made its first landfall on the island of Barbuda with 185 mph winds early Wednesday, and is expected to roar through the U.S. Virgin Islands, Puerto Rico and other Caribbean islands next.

NOAA hurricane hunters flew through the eye of Hurricane Irma on Sept. 5, capturing the storm's massive eye wall on camera. (Reuters)

The National Guard Bureau has alerted thousands of Guard members that they may be needed, Davis said. The National Guard has about 5,200 members in Puerto Rico, 650 in the U.S. Virgin Islands and more than 7,000 in Florida, all of whom are in the path of the storm. Scott activated the Florida National Guard on Tuesday, and anticipated that the entire force would be on duty by Friday.

Army Sgt. 1st Class Michael Houk, a National Guard spokesman, said that the bureau has flown teams to Puerto Rico and Florida that will act as liaisons with local governments in coordinating outside help.

“We have a very deep pool of guardsmen from other states to draw from as we work with our local, state and federal partners in response to this storm,” he said.

The Defense Department could require two regional combatant commands to respond to the hurricane. The U.S. Southern Command, led by Navy. Adm. Kurt Tidd, oversees operations in Caribbean Islands that include Cuba, Haiti, the Dominican Republic, Jamaica, Antigua and Barbuda. U.S. Northern Command, led by Air Force Gen. Lori Robinson, commands operations in the Bahamas, Puerto Rico and other points north of Cuba, including the continental United States.

The storm has prompted defense officials to examine the situation closely at the Navy’s base at Guantanamo Bay, Cuba, where the U.S. has long kept a detainment center that holds accused terrorists, including Khalid Sheikh Mohammed, the alleged principle architect of the attacks on Sept. 11, 2001.

A Pentagon spokesman, Air Force Maj. Benjamin Sakrisson, said Wednesday that the Defense Department is “acutely aware of the need to ensure the safety and security” of detainees at Guantanamo during the storm.

“Tropical weather is an expected part of life in the Caribbean and for our personnel charged with securing the detainee facilities,” Sakrisson said. “Likewise, they routinely prepare for any contingencies required to safeguard all individuals at the installation in the event that extreme weather impacts the region. There is no intent for the safety of the detainees to come into question during Hurricane Irma.”

Further complicating the hurricane response will be the ongoing evacuations. Army Col. Lisa Garcia, a Southern Command spokeswoman, said Wednesday that nonessential personnel are departing the command’s headquarters west of Miami in Doral, Fla., to prepare for the storm, and the Navy announced Tuesday that it is removing about 5,000 personnel from Naval Air Station Key West, leaving a few dozen to keep the base running.

“We will maintain a watch team here at the HQ throughout the weekend to monitor Irma and coordinate should we receive a request to support the region,” Garcia said of Southern Command’s headquarters in an email Wednesday.

The Air Force has relocated 21 of its F-16 fighters from Homestead Air Reserve Base south of Miami and C-130 cargo planes and nine HH-60 Pave Hawk helicopters from Patrick Air Force Base, Fla., said Erika Yepsen, a service spokeswoman.

The service also is preparing for the 53rd Weather Reconnaissance Squadron at Keesler Air Force Base in Mississippi — commonly known as the “Hurricane Hunters” — to deploy later this week to monitor the storm, and has moved search-and-rescue teams that responded to Hurricane Harvey to their home bases so they can recover in advance of the new hurricane, he said.

As the path of the storm becomes more clear, the Pentagon also could establish specific installations as hubs for the recovery effort, Davis said. They could range from Joint Base Charleston in South Carolina to Eglin Air Force Base in the Florida Panhandle, but it is too early to say which will be selected, he said.

The Coast Guard also is gearing up for Hurricane Irma, and began transferring helicopters from Texas, where they were involved in the response to Harvey, to Florida and Puerto Rico beginning last Friday. The service has Florida air stations in Clearwater, Miami and Key West, and one in Puerto Rico at Borinquen, on the northwestern coastline.

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