WASHINGTON • As White House deputy chief of staff for operations, Mr Joseph Hagin oversees a staff of some 4,000 across communications, logistics, security and Air Force One operations.
There are probably few political appointees who have worked more years in the White House than the low-profile 62-year-old from Ohio, who is known to have a deep reverence for and sense of duty to America's institutions of government. He served in the administrations of both President George H.W. Bush and his son, President George W. Bush.
He was there amid the rubble of the Twin Towers three days after the Sept 11, 2001 terrorist attacks, when the younger Mr Bush climbed on a flatbed truck and shouted through a bullhorn: "The people who knocked these buildings down will hear all of us soon."
Later, "Big Joe" - as President George W. Bush used to call him - was put in charge of the team that created the powerful Department of Homeland Security.
In between serving Republican presidents, he held senior corporate positions at big private sector names such as Chiquita Brands and Federated Department Stores.
Ms Alyssa Mastromonaco, who was deputy chief of staff for operations under President Barack Obama, said last year: "Joe has an excellent reputation among the (White House) career and military staff.
"When Trump hired him, I enjoyed a moment of peace thinking we were in good hands."