If the Americans were going to attack Iran, you'd think they would do it when they had a ship or two available. Various people have been getting their knickers in a twist because the Dwight D. Eisenhower and her task group sailed for the Indian Ocean on the 3rd of October. (The Nation, this means you.) There is a carrier group there already, around the Enterprise. Apparently this is a gathering armada and proof that Teh October Surprise is planned.
One problem. US aircraft carriers work on a six-month operating cycle. When did Enterprise and Co. leave for the Indian Ocean and the Gulf? The 2nd of May. When did she arrive on station? A month later, on the 3rd of June. When is she due back in Norfolk? The 3rd of November, clearly. When must she leave her station? Now, or thereabouts. When must Eisenhower leave to relieve her? Well, the 3rd of October. Clearly.
Further, look at the rest of the fleet. Out of 11 ships, 5 are currently unavailable - 4 out of 10, if you count the nearly-decommissioned John F. Kennedy. Carl Vinson, George Washington, Harry S. Truman, and Abraham Lincoln are all in dry docks and not going anywhere. The rest are not much more available.
Operating a nuclear-powered carrier is not simple. Each ship is a military airbase, indeed a small air force with the complete spectrum of aircraft roles and its own maintenance, a considerable headquarters and radar centre, a nuclear power station, a hospital and a barracks, sailing across the high seas. Unlike sensible nations, the US Navy thinks conventional aircraft should be used on ships, which means that they must be catapult launched and must land into a big steel cable. The whole thing makes the International Space Station look like a Citroen 2CV.
Hence, they work to an immovable rota of training and maintenance. To deploy, a carrier must finish its dockyard schedule and then accumulate a succession of ticks in the right boxes. The first is proficiency training for the crew. Then comes carrier qualification (CARQUALs) for the air wing - practice landings. Then comes a three-week long Composite Training Unit Exercise (COMPTUEX) for the whole ship. Finally, another three-week tactical exercise called a Joint Task Force Exercise (JTFEX) for the ship, the task force and the air wing. Then the ship is, as they say, ready in all respects and may proceed to sea.
Over time, the schedule is meant to provide a constant level of readiness, but these things are never perfect and hence the actual results wander. Also, something like..a war..can disrupt the whole thing. In late 2001, some 5 carriers were sailed in short order, and then in late 2002 a 3-carrier task force was gathered to attack Iraq. The repercussions are still working through.
In detail, then. Enterprise is due to return and will probably need to take on stores before any attack. Eisenhower has sailed to relieve her. The ships given above are completely immobile, and only one of them could be pulled out of dockyard hands in a serious crisis. ("Serious" here means Pearl Harbour.) Theodore Roosevelt is doing her CARQUALs and is therefore unready for at least two months, even if the training programme could be undertaken without any time between exercises. Ronald Reagan is also in CARQUALs. Nimitz hasn't even begun hers, and is currently tied up in San Francisco for Fleet Week.
The John C. Stennis is in the second week of her COMPTUEX, so even if she was sailed without doing a JTFEX she would miss the supposed target date. That only leaves Kitty Hawk in Japan, the forward-deployed carrier. She is the coalmine canary, but is as far as I know singing a healthy song.
What of the Royal Navy? Most of it, including 2 out of 3 assault ships, is currently steering for Sierra Leone for a joint amphibious exercise (and show of strength ahead of Charles Taylor's trial), Ex VELA 06. It's almost like someone was trying to put it as far from the Gulf by sea as is reasonably possible. HMS Illustrious returned from an earlier deployment to the Arabian Sea on the 3rd of August. Ark Royal is on sea trials having left Babcocks in Rosyth on the 2nd October - she isn't due in the Fleet until December. Invincible is effectively mothballed.
There are also the US Marines to think of. Any operation against Iran would likely need three carriers and at least one, possibly two, Marine Expeditionary Strike Groups. So where are they? One is on station in the Middle East and another in Japan. And the Bonhomme Richard group is in San Francisco.
There will be no attack on Iran. Amateurs discuss tactics, professionals study logistics, right? It's just a pity that, six months ago, everyone got all het up and they haven't noticed a pattern.
Update, Revised and Extended: Multiple commenters here and at highclearing.com following the Henley-alanche dropped on this post have asked whether an operation against Iran could be mounted from land bases alone. For a start, I'd refer you to Comments Dan's comment. But to unpack a little, it's impractical. The US does not, contrary to popular belief, possess a wealth of air bases in the Gulf. The biggest is in Qatar, which is (as Dan notes) unavailable - Qatar even voted with Iran in the UNSC. There are field, forward bases in Iraq, which do not provide enough capacity and are heavily in use for tactical air operations in Iraq. Afghan bases will only provide a limited number of sorties, as the support infrastructure is, as they say, austere (i.e. there's a runway but bugger all else). The RAF's Tornado GR4 fleet, for example, cannot be used to support British forces in Afghanistan because the runway at Kandahar is too short, and the Jaguar fleet cannot be deployed because, at that altitude, they cannot take off with a useful load.
This leaves Diego Garcia and Ali Al Salem in Kuwait. One of these is a long way from the fight. Beyond these, there are of course the USAF's long-range bombers, the B-52s and B-1Bs. However, the first cannot be used over Iran until the Iranian air defences are tackled, and the fleet of the second can't do it all on its own. Also, many of the putative targets are said to be fortified or underground, which means that the warhead on a Tomahawk missile cannot be expected to penetrate them. Therefore, any attack will need a considerable number of sorties by fighter-bomber types to suppress air defences before large bombers can be brought in. That requires bases close to the battlefield, and without host-nation support this means carriers.
Much of the airpower boosterism of the last few years has been the product of the unusually permissive environment of Iraq and Afghanistan, which has permitted large targets like B52s to loiter in enemy airspace waiting for the call to drop JDAMs. This cannot be assumed over Iran, which has been investing heavily in modern SAMs and maintains a significant but unknown modern fighter capability. Specifically, we don't know at all what (if any) capability they have to attack high-value air assets like AWACS, Rivet Joint, JSTARS, and tankers. If their small fleet of F14s is operational and the AIM54 missiles usable, or reverse engineered, this could be a serious problem.
Update again: When the Nimitz swung into San Francisco, we were able to get a blogger aboard for an on-site inspection. If you like ships you'll love the photos.