The details of how and when the U.S. military and allied forces might attack are under debate but would be based on complex plans developed and repeatedly reworked over time by the Pentagon.
A look at what's known and what's unclear about how it might unfold:The order for the strike would come from Obama, delivered to Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, and Defense Secretary Chuck Hagel. The operation probably would fall under the purview of U.S. Central Command, headed by Army Gen. Lloyd Austin. The more immediate commander probably would be Adm. Bruce Clingan, who heads U.S. naval forces in Europe.
U.S. commanders would communicate and coordinate with military officers from other nations involved in the fight, such as France.Five U.S. Navy destroyers – the USS Gravely, USS Mahan, USS Barry, the USS Stout and USS Ramage – are in the eastern Mediterranean Sea waiting for the order to launch.
They are armed with dozens of Tomahawk cruise missiles, which have a range of about 1,000 nautical miles and are used for deep, precise targeting. Each one is about 20 feet long and less than two feet in diameter and carries a 1,000 pound warhead.
The USS Stout just arrived, and it's not clear yet how long the Navy will keep all five destroyers there, or whether it will release the Mahan, which had been scheduled to return home.
The missiles fly at low altitudes, and their range allows the ships to sit far off the coast, out of range of any potential response by the Syrian government. Some ships have cameras that can provide battle damage assessments.
The Navy also now has two aircraft carriers in the Arabian Sea that are loaded with fighter jets. The USS Truman arrived in the region to take the place of the USS Nimitz, which was supposed to head home. But the Navy ordered the Nimitz to stay for now.
With Britain on the sidelines, France has said it is preparing for military action against Syria. French President Francois Hollande does not need parliamentary approval to launch a military operation that lasts less than four months.
French military officials confirmed the frigate Chevalier Paul, which specializes in anti-missile capabilities, as well as the hulking transport ship Dixmude, had set off Thursday from the Mediterranean port of Toulon as part of normal training and operational preparations.
France also has a dozen cruise missile-capable fighter aircraft at military bases in the United Arab Emirates and the Horn of Africa nation of Djibouti.Obama has ruled out putting troops on the ground in Syria, and because of Assad's extensive air defense systems, officials believe it is too risky, at least initially, to deploy fighter aircraft or even low-flying drones that could be shot down.Dempsey has told Congress that lethal force would be used “to strike targets that enable the regime to conduct military operations, proliferate advanced weapons and defend itself.”
At a minimum, Western forces are expected to strike targets that symbolize Assad's military and political might: military and national police headquarters, including the Defense Ministry; the Syrian military's general staff; and the four-brigade Republican Guard that is in charge of protecting Damascus, Assad's seat of power. Assad's ruling Baath Party headquarters could be targeted, too.
U.S. officials also are considering attacking military command centers and vital forces, communications hubs and weapons caches, including ballistic missile batteries.U.N. inspectors were scheduled to leave Syria today.
There has been a so-far unsuccessful effort to seek U.N. Security Council approval for a strike, but there is also significant pressure on the administration to act quickly and decisively.
Any military operation would probably unfold at night or in the predawn hours in Syria, with an initial assault possibly lasting several hours and involving dozens of missile strikes from several warships.
What could follow is a period in which the U.S. would use satellites and other intelligence capabilities to assess the damage.
Such an assessment could be followed by an additional round or two of missile strikes, if ordered by the president.