Defense Secretary Pete Hegseth has fired Navy Secretary John Phelan. The Pentagon framed it Wednesday as an immediate departure. Why it matters: The ouster of the Navy's top civilian caught many off-guard and adds to the pile of military officials who have either abruptly exited or been pushed out of their posts under Trump 2.0. " Phelan didn't understand he wasn't the boss. His job is to follow orders given, not follow the orders he thinks should be given," a person familiar with the situation told Axios. The same person said Phelan and Hegseth did not "get along." Driving the news: Chief Pentagon spokesperson Sean Parnell said Phelan was "departing the administration, effective immediately," in a post on X . He did not provide a reason. Navy undersecretary Hung Cao will take over in an acting capacity. The intrigue: Phelan and President Trump are said to have a good relationship. The two have texted about rust on warships.…