On Sunday, White House National Security Advisor John Bolton announced that those military resources were responding to credible intelligence regarding Iranian plans for attacks on American assets and allies both on land and at sea. The aircraft carrier, the USS Abraham Lincoln, was already scheduled to arrive in the region as part of a dynamic deployment, but the US Navy’s Central Command confirmed that that schedule had been accelerated in response to the apparent threat. It is currently en route.

Bolton’s reference to the relevant intelligence was generally vague, and little concrete detail was provided by Shanahan or Dunford when speaking to a Senate Appropriations defense subcommittee. But both men did attempt to explain the context surrounding their acquisition of that intelligence.

“We received indications of this very, very credible intelligence on Friday afternoon,” Shanahan said, adding, “We went to work understanding the sources and to get the teams turning on ‘What does it mean?’ and how might we respond.”

Dunford then noted that the Defense Department immediately went to work on making sure that the US was “postured to respond to the threat,” although the announcement of that response only emerged two days later.

As well as reporting upon this testimony, ABC News noted on Wednesday that it had “learned that the intelligence including indications that Iran or its proxies were planning attacks against US forces in Iraq, Syria, and at sea.”

The threat and subsequent response naturally come at a time when tensions between Iran and the US are already escalating. On Monday, in immediate response to Bolton’s announcement, The Atlantic published an article assessing some of the ways in which Iran might attempt to do harm to American personnel, interests, or allies if the tensions escalated to the point of actual conflict. Both governments have provided public assurances that they are not interested in war, and this was a prominent aspect of Bolton’s statement. But Tehran has also directed militaristic rhetoric against its adversaries, which might serve as a pretext for action by any of the various proxies the Islamic Republic controls and supports.

This was arguably the implication of the statement that Foreign Minister Javad Zarif made via Twitter on Tuesday, in response to the news of the Lincoln’s deployment. “If US and clients don’t feel safe, it’s because they’re despised by the people of the region,” he declared, thereby distancing the Iranian regime from whatever intelligence underlay the deployment. But historically, many of the groups that have taken up arms against the US, including Hezbollah, Iraqi insurgents, and Syrian loyalist forces, have relied heavily on Iranian supports in order to do so.

This situation was affirmed by Ali Vaez, an expert on Iran at the Crisis Group, who was quoted in The Atlantic’s risk assessment article. “The Iranians have plenty of experience targeting U.S. forces in the region indirectly through the use of their Shia militia allies,” he said. And according to Vaez, the current presence of 2,000 US service members in Syria, 5,000 in Iraq, and 14,000 in Afghanistan means the US is “very much exposed” to further attacks along these lines.

It is not clear, however, to what extent Tehran would risk even an indirect attack in the presence of active deterrence by the US and by Iran’s regional adversaries. Meanwhile, it is even more doubtful that the regime would risk direct military confrontation, despite the fact that officials have repeatedly threatened to close the Strait of Hormuz in response to US-led efforts to constrain the country’s oil exports.

The website Statista responded to emerging concerns about the potential for conflict on Tuesday by assessing the strength of the Iranian military. It noted that although an estimated 900,000 active-duty personnel present a significant threat, that threat is greatly diminished by the fact that Iran’s military equipment is outmoded and largely dates back to the time of the Shah, before the 1979 Iranian Revolution. Furthermore, because the current regime has struggled to obtain components that are necessary for the maintenance of that equipment, many of Iran’s military vehicles “have been left inoperable.”

On the other hand, this is not to say that Tehran has been completely unsuccessful in expanding upon the direct threat that it poses to adversaries. The current leading source of that threat is the regime’s missile program, which was highlighted in an article that originally appeared at the National Interest late last year, but was reposted on Monday in the wake of Bolton’s announcement.

The report noted that Iran had actually used some of its more advanced missiles in attacks upon enemy groups in Syria last September and in Iraq last October. But in spite of ongoing advancements, the range of Iran’s ballistic missiles reportedly remains limited to approximately 1,200 miles. Additional, that missile program has become a major focus of the Trump administration’s efforts to rein in Iran through “maximum pressure” via economic sanctions and diplomatic intervention.

Exactly one year ago Wednesday, President Donald Trump withdrew the US from the 2015 Iran nuclear deal, citing ballistic missile production and testing as one of the leading means by which the clerical regime had violated the “spirit” of the agreement.