Naval fleets are predominantly created and organized for power projection, taking the fight to the enemy on their turf to ensure that American are safe at home. But the U.S. Navy and Marine Corps do practice defending the fleet at sea should it come under a direct attack.
Here's how they do it:
The guided-missile cruiser USS Normandy (CG 60) fires its Phalanx close-in weapons system during live-fire training exercises in the Atlantic Ocean on August 31, 2018.
(U.S. Navy photo by Mass Communication Specialist 3rd Class Michael Chen)
The Navy has a number of weapons that are custom designed for protecting ships and personnel. Perhaps one of the most famous of these is the Phalanx Close-In Weapons System. This is the final, goal-line defense against anything above the waterline. Basically, it's R2-D2 with a 20mm, multi-barrel gun.
The Phalanx is typically associated with cruise missiles, and that's because it's one of the few weapons that can destroy cruise missiles in their final attack. But it's also perfectly capable of attacking other threats, especially slower-moving items in the air, like planes and helicopters.
The Ticonderoga-class guided-missile cruiser USS Mobile Bay (CG 53) travels alongside the Nimitz-class aircraft carrier USS John C. Stennis (CVN 74) during a replenishment-at-sea.
(U.S. Navy photo by Mass Communication Specialist 3rd Class William Rosencrans)
Of course, the Marines aren't content to wait for threats to approach the Navy's Phalanx, and so, on larger ships like LHAs and LHDs, the Marines can drive their vehicles onto the decks and fire the guns off the ship, striking attack boats or enemies on nearby shores with anything from the .50-cal. machine guns to 25mm Bushmaster cannons to rounds from a 120mm Abrams cannon.
All of that's in extremis, the-enemy-is-at-the-gates kinda of defense. The next ring out is provided by cruisers and destroyers who try to keep all the threats away from the heart of the fleet.
The beefier of these two is the cruiser. For the U.S. Navy, that's the Ticonderoga class. It has 122 vertical-launch cells that can fire a variety of missiles. Lately, the Navy has been upgrading the cruisers to primarily fire the Navy's Standard Missile-3. This baby can hit objects in space, but is predominantly designed to hit targets in the short to intermediate ranges from the ship.
The guided missile destroyer USS Dewey (DDG 105) conducts a tomahawk missile flight test while underway in the western Pacific.
(U.S. Navy Mass Communication Specialist 2nd Class Devin M. Langer)
But the Ticonderogas, and their destroyer sisters, the Arleigh-Burkes, can also carry Tomahawk land-attack cruise missiles, Standard Missile-2s, and Evolved SeaSparrow Missiles. Need to hit something below the waterline? Try out the ships' Mk. 46 or Mk. 50 torpedoes. Both ship classes can fire the torpedoes via rockets, and the Ticonderoga can fire them directly from tubes.
The Tomahawk is the weapon that really increases the fleet's range, hitting ships at ranges of almost 300 miles and land targets at over 1,000 miles. As attackers get closer, the fleet could start firing the shorter range weapons, like the anti-submarine rockets and SeaSparrows.
But there's an overlap between the Tomahawks' range and that of the fleet's most powerful and longest-range protection: jets. The carrier groups and amphibious readiness groups have the ability to launch fighter and attack jets. As time marches on, these jets will be F-35Bs and Cs launching from carriers and Landing Helicopter Assault and Landing Helicopter Dock ships.
A U. S. Navy F/A-18E Super Hornet launches from the Nimitz-class aircraft carrier USS Harry S. Truman in the Norwegian Sea, October 25, 2018.
(U.S. Navy photo by Mass Communication Specialist 3rd Class Adelola Tinubu)
For now, though, its mostly Navy F/A-18 Super Hornets taking off from carriers and Marine Corps AV-8B Harriers taking off from the LHAs and LHDs. The Harriers can only reach out to 230 miles without refueling, but the Hornets have a combat radius of over 1,000 miles without refueling.
And both planes can refuel in the air, usually guzzling gas from modified Super Hornets, but the Navy is working on a new, specialized drone tanker called the MQ-25 Stingray.
The Super Hornets pack 20mm cannons as well as a variety of air-to-air missiles, air-to-ground missiles and bombs, but their greatest ability to cripple an enemy attack comes from another plane: The E-2 Hawkeye.
An E-2C Hawkeye, assigned to Carrier Airborne Early Warning Squadron, approaches the aircraft carrier USS George H.W. Bush.
(U.S. Navy Mass Communication Specialist 3rd Class Roland John)
The Navy's E-2C Hawkeye Airborne Early Warning and Control plane is unarmed and slower than most of its buddies in the sky, but it's a key part of the Navy's fleet defense and offense thanks to its massive radar. That radar can see out 340 miles and track over 2,000 targets. It can actively control the interception of 40 targets, helping guide friendly fighters to the enemy.
So, when the Navy's fleets come under attack, enemies have to either catch them off guard, or fight their way through the concentric rings. Their land-based assets are susceptible to attack from over 1,000 miles from the fleet thanks to ground-attack aircraft and Tomahawks. Their ships are vulnerable at similar ranges from aircraft and 300 miles from the Tomahawks.
As they draw closer, they face SeaSparrows and Harpoon anti-ship missiles, and their fighters can come under surface-to-air missile attacks from the Standard Missile-2. If they actually draw within 20 miles, they start facing the Navy's deck guns and torpedoes. A short time later, the Marine get in on the fight with their vehicles driven up onto decks.
A Los Angeles-class fast attack submarine participating in Exercise Keen Sword with Submarine Group 7 and Japan Maritime Self-Defense Force sailors and staff.
(U.S. Navy photo by Chief Electronics Technician Robert Gulini)
And all of that's ignoring the possibility that a nuclear submarine is in the water, just waiting for a surface contact to fire their own torpedoes at.
Of course, a determined enemy could use their own large fleet to push through those defenses. Or, a crafty enemy could wait for a fleet to transit a chokepoint and then attack from the shore or with a large fleet of fast attack craft.
That's the kind of attack the U.S. fears from Iran in the Straits of Hormuz. At it's most narrow point, the strait is only 35 miles wide. U.S. ally Oman is on one side of the strait, but that still leaves any ships passing through within relatively easy range of Iran, even if they're hugging the Omani shore.
The expeditionary mobile base platform ship USS Lewis B. Puller transits the Strait of Hormuz, Oct. 22, 2018.
(U.S. Navy photo by Mass Communication Specialists 3rd Class Jonathan Clay)
And so, fast attack craft from Iran would be able to target one or two ships as they pass through the Strait, sending dozens of speedboats against the ships, preferably while those ships armed with Phalanxs and missiles are out of range or blocked by other vessels.
And that's why the Navy makes such a big deal about chokepoints, like the Straits of Hormuz, or certain points in the South China Sea. Multi-billion dollar assets with thousands of humans aboard, normally well-protected at sea, are now within range of relatively unsophisticated attacks from American adversaries.
So, while the Navy needs to protect its fleets at sea, that's the relatively easy part of the equation. The scarier proposition is taking an attack near hostile shores or being forced to sail into range of the enemy's shore-based aircraft, where the fleet's overwhelming firepower finds a strong counter that could cripple it.