As American officials circulated photographs of Iranian boats traversing the Arabian Gulf bearing missiles, there was a growing consensus on Friday that Tehran had been caught red-handed.
Experts are divided on whether the images show already reported activity or a new clear and present danger to free passage in the straits.
“Reports that Iran was loading missiles on boats are certainly credible. After all, it is not the first time. There is good evidence that Iran has previously supplied missiles to Houthi rebels by sea,” said Mark Fitzpatrick from the International Institute for Strategic Studies.
That Iran has “plenty” of coastal combat boats was not in doubt, added Erwin van Veen from the Clingendael Institute – but the question, he said, was if the pictures represented a step change in the threat level.
Peter Waring, an analyst at consultancy Ridgeway Information, said Iran has a formidable maritime and littoral capability in the Arabian Gulf and a track record of targeting vessels at times of tension.
"Assuming that the New York Times assessed the imagery, the reports do appear credible," he said. "The reporting I've seen are somewhat contradictory but given the small size and carrying capacity of dhows, it is likely that the missiles in question are the Noor anti-ship missile. These weapons have – according to some reports – already been used on the Saudi side of the Gulf by Houthi rebels.
“It can be assumed – by the use of Iranian missiles previously by Houthi rebels in Yemen against targets in the UAE and Saudi Arabia – that these weapons have been smuggled across the Gulf for some time.”
Mr Fitzpatrick, a former US State Department official, said it was far less credible that Iran would seek to fire from the boats, citing the difficulty of firing accurately. “Iran would have no reason to do so, because it has ample on-shore locations from which to fire,” he said.
Nicholas Heras, Middle East Security Fellow at the Centre for a New American Security and Senior Analyst at Jamestown Foundation, said the Iranians did see an advantage in force projection across the water. The Islamic Revolutionary Guard Corps (IRGC) has adopted so-called swarm tactics with small boats to harass US Navy vessels in transit.
“The US military does not mess around when it comes to evidence of this nature that could later be used as a casus belli,” he said. “A great concern for the US, and its Gulf Arab partners, is how the IRGC could use the maritime domain to support its proxies, to close off international maritime shipping, or even significantly damage or destroy US and partner vessels. Iran sees the maritime domain as an arena where it can fight the US at something like parity, and where it can undermine close US partners like Bahrain. This is a grave situation.”
But President Donald Trump has also reportedly told senior cabinet officials that conflict is not something he seeks. Analysts argue that he is trying to pressure Iran into talks where they have the weak hand.
“It’s very hard to tell – either Iran really was preparing some retaliation, or the Trump administration wants it to have been, and to present it as being true,” said Patrick Porter from the Royal United Services Institute.
Arshin Adib-Moghaddam from SOAS in London said “so-called evidence of Iranian escalations” was merely part of a US campaign combining “psychological warfare and gunboat diplomacy” to push Iran towards the nuclear negotiating table once again.
Mr Porter said in some ways the surge in tensions resembled a Gulf version of the North Korean crisis in August 2017 where Mr Trump said Pyongyang would be met with "fire, fury and frankly power, the likes of which the world has never seen”, as the regime continued its nuclear testing.
Ultimately and perhaps surprisingly, relations between the two countries thawed for a period of time, although this was less likely in the case of Iran, argued Mr Porter.
He said President Hassan Rouhani was “far less incentivised to talk to Trump than Kim with Trump” whereas as North Korea “craved a presidential summit with Washington for decades”.
“Iranian leaders who so much as talk to a US president on the phone get in trouble domestically,” he added.
If, however, US and Iranian officials do get around the table, do not expect it to simply be a capitulation for Iran, warned Chatham House’s Sanam Vakil.
“I believe President Trump wants negotiations with Iran and that it is his end game. What he might not being doing so well is creating an environment to facilitate those negotiations,” she said. “Iran is trying to build some leverage, be on more equal ground and is looking to see a change in American behaviour, policy, language, dialling down of some its demands on Iran.”
“The president and his advisers seem to think that maximum pressure is the best way to communicate with Iran. I don't think that's very productive,” added Ms Vakil.