President Trump revoked security protection for his former secretary of state, Mike Pompeo, and a former top aide, Brian Hook, despite warnings from the Biden administration that both men faced ongoing threats from Iran because of actions they took on Mr. Trump’s behalf, four people with knowledge of the matter said on Thursday. Mr. Pompeo and Mr. Hook had been part of an aggressive posture against Iran during the first Trump presidency, most notably the drone strike that killed the powerful Iranian general Qassim Suleimani in early 2020. Mr. Trump also remains under threat because of that action, and his...