Lt. Gen. Dan Caine’s pocket-size copy of the Constitution is tattered and bound with green military tape.

He carries it with him routinely, including slipping it in his flight suit when he flew fighter jets in the Air Force. He had it on him on Sept. 11, 2001, when he was the lead aviator assigned to protect Washington after hijackers slammed commercial jets into the Pentagon and the World Trade Center.

General Caine’s loyalty to the Constitution and his reputation for adhering to ethical standards are major reasons the Senate Armed Services Committee is likely to give him a largely friendly reception on Tuesday as the members consider his nomination to become the chairman of the Joint Chiefs of Staff, the nation’s highest-ranking military position.

General Caine’s writings, coupled with interviews with some who know him, paint a portrait of a modest, thoughtful and personable officer with a reputation for integrity. That sets him apart from some other high-ranking administration officials who often appear to place their fealty to the president above all else.

“He has strong moral fiber,” said Raj Shah, who led a high-level Defense Department unit on innovation and has known General Caine for 20 years. He added, “He is one of the most humble, principled and strategic leaders I have known.”

But General Caine will still have to navigate some tough questions about whether he will give his best unvarnished military advice to President Trump or tell him what he wants to hear.