I don't know enough about the current state of naval warfare but I've assumed this is related to the asymmetry that's emerged around protecting capital warships, especially in the scenario of a very narrow strait and a long enemy-controlled coastline. They can shoot relatively low-cost, short-range guided missiles from anywhere along the coast. Even if a warship stops the vast majority of them, only one has to get through to sink a multi-billion dollar ship that takes a decade to replace.
There are now similar asymmetries emerging across war-fighting and even though warships can still be effective (and less vulnerable) in other scenarios, this specific one seems especially bad. The other factor is that most of what ships carry through the straight isn't going directly to the U.S. so the impact on the U.S. is mostly secondary, reducing the risk the U.S. is willing to take. Of course, all this was known beforehand by military strategists which makes this all look even worse for the U.S. administration.
Modern US surface warships such as the DDG-52 Arleigh Burke class are pretty survivable. The Iranians (and their Houthi proxies) have made sustained attacks on them and don't seem to have hit anything. And a single hit would be highly unlikely to sink such as vessel: we're not talking about something like the Russian Moskva cruiser that was crewed by drunks and had inoperative defensive systems.
The real problem is that there are too few such vessels to sustain convoy escort operations. Each destroyer can only provide area air defense for a handful of merchant vessels, and they can only stay on station for a few days at a time before they have to cycle out to refuel, rearm, and conduct critical maintenance. Some of the key munitions also appear to running low. And it appears that the other Gulf states are refusing to allow use of their facilities over fears of Iranian retaliation.
Other countries generally aren't really in a position to assist as part of a coalition either. They either don't have sufficiently capable warships at all, or lack the logistics train to sustain them in the Persian Gulf / Gulf of Oman region. After the Cold War a lot of countries like the UK and Germany essentially dismantled their navies so that they now exist only as government jobs programs.
> I don't know enough about the current state of naval warfare but I've assumed this is related to the asymmetry that's emerged around protecting capital warships, especially in the scenario of a very narrow strait and a long enemy-controlled coastline.
It's not the billion-dollar warships that transport oil, it's the much more fragile and unarmed tankers.
Even if the US Navy begins full escort duty, it can't remain on-station forever. What are shippers to do afterwards? One drone strike might cause a tanker to have a very bad day, yet it's extremely difficult to so permanently degrade an entire country that they become incapable of launching sporadic attacks.
Ultimately, the status of the Strait must be settled diplomatically, and the US and Iran are each betting that the other side will blink first.
Cheap drones taking out an AWACS is a great example of this. The US has only 16 of these and it will cost $700 million to replace, and was taken out by a drone that probably cost less than your car.
All of this was well known before the war though. The idea that navy is incredibly vulnerable modern anti-ship defenses has been a major consideration in the Taiwan situation for at least a decade (mostly in relation to the ability of the US navy to even operate in the area in a war). More recently, Ukraine has made a great show of sinking navy ships with cheap unmanned surface vehicles
Back in WWII you could sail your navy up a river and expect positive results. In the 21st century, the idea of attacking an enemy-held strait with navy doesn't work
The US military is also just less powerful than it was at its peak at the end of the Cold War as well.
Still the most powerful navy in the world, but spread increasingly thin (turns out "the whole world" is quite a big place).
This is no longer Reagan's (almost) 600 ship navy, and projecting power halfway round the world is no mean feat when your opponent can lob missiles and drones at you from their back garden
suppose one has N independently developed interception systems (from detection till physical interception attempt), each with an intercept success rate of 90%.
a rudimentary calculation then gives the probability of hitting (not sinking) the ship as 0.1^N per launched missile; so it seems that given enough budget to spend on independently developed missile interception systems allows to drive down the penetration success rate arbitrarily.
Multi-billion sounds like $ 10^10; so assuming an attacker can launch say a million missile attempts then the statistical loss would be 0.1^N * 10^10 * 10^6; so the statistical loss can be driven down arbitrarily say to $ 1 by developing ~ 16 independent interception systems.
16 independently developed intercept systems doesn't sound like unobtainium for a vested nuclear power.
furthermore, the development cost of 16 independent intercept systems can be amortized over many more installations than a single ship, it can be amortized over multiple ships, multiple bases, multiple strategic assets across the globe.
> Even if a warship stops the vast majority of them, only one has to get through to sink a multi-billion dollar ship that takes a decade to replace.
Even worse. They don't need to attack _warships_. They can just attack civilian vessels, especially tanker ships, that don't have any defenses.
A hit on a tanker and the subsequent oil spill would be catastrophic.
The bigger issue is the tankers. The US Navy isn't going to be happy patrolling the strait sure, but even if they did they wouldn't be able to protect the tankers enough for it to make sense for tankers to take the risk.
The last time this happened the US opened the strait by accidentally shooting down an Iranian passenger plane after sinking a large chunk of Iranian navy. The Iranians assumed the US shoot the passenger plane down on intentionally as a war crime and assumed the US would was planning to escalate the conflict. This fear deterred further Iranian attacks on tankers.
This isn't going to work this time because the US started the war by performing of the most serious escalations possible, a decapitation strike against top Iranian leadership in a surprise attack using a diplomatic negotiation as cover. The US did this while the strait was open and Iran was considering a peace deal.
Threats of escalation are no longer effective at deterring Iran because Iran now believes the US will take such actions regardless of what Iran does. What does Iranian leadership have to lose by staying the course? Very little. On the other hand if Iranian leadership back down, they loose all their leverage, they look weak internally, they look weak externally and the US might decide to attack them out of the blue again.
This is why decapitation strikes are generally not done. They remove options and they undermine deterrence and paint belligerents into a corner.