Read: Pay attention to what the U.S. is doing to Iran

Administration officials have not so far disclosed what exactly prompted the worries about Iran targeting the U.S. or its allies, with Acting Secretary of Defense Patrick Shanahan, for instance, only citing “indications of a credible threat by Iranian regime forces.” Still, the dynamics of the region, and especially how deeply entrenched both Iranian and U.S. forces are there, have left the Iranians with plenty of opportunities to harass America and its allies if they choose.

Iranian forces or their proxies operate close by U.S. and U.S.-backed forces in both Iraq and Syria. Iran routinely threatens to disrupt the world oil trade through the Strait of Hormuz off its coast; its aligned forces in Yemen and the Gaza Strip directly threaten U.S. allies in Saudi Arabia and Israel with rocket attacks.

The carrier strike group (CSG) that Bolton announced was headed to the Middle East had actually departed for a scheduled deployment more than a month ago. “Carrier deployments take some time to plan and aren’t sudden decisions, although their course is more flexible,” Becca Wasser, a policy analyst at the RAND Corporation, wrote in an email. “Bolton’s statement merely leveraged an existing and ongoing deployment to send a message to Iran. It is important to note that he or the White House did not suddenly order the CSG to deploy.”

The chief of naval operations, Admiral John Richardson, confirmed as much to reporters at an event Monday, according to U.S. News & World Report, though he later tweeted that the carrier strike group would go to the Middle East “at the direction” of Bolton and Shanahan. Wasser wrote that U.S. military strategy now calls for more unpredictability to confront rivals like Iran. “The U.S. Navy—and all services—has adopted dynamic force employment to demonstrate flexibility and the ability to respond to contingencies and world events as they unfold,” she wrote.

Read: Trying to kill the Iran deal could end up saving it

As harsh rhetoric escalates on both sides, so does the potential for miscalculation. When the Trump administration declared the Islamic Revolutionary Guard Corps a terrorist group, it hoped to render internationally “radioactive” Iran’s dominant security service, which is also a major economic actor. But in announcing the move, Secretary of State Mike Pompeo declined to specify whether the designation, which opens the door to U.S. criminal penalties for anyone doing business with the IRGC, made the group to subject targeting by U.S. forces in the region; a Department of Defense spokesperson told us then that the rules of engagement had not changed. Iranian-backed forces, according to U.S. officials, were responsible for killing more than 600 American service members from 2003 to 2011, but they have uneasily shared the same battle space on the same side against the Islamic State in Iraq and Syria since 2014, and even at times collaborated.