Nobody realised, until he withdrew his nomination as defence secretary, that he was also an insecure and vulnerable man who could be deeply wounded by criticism.
His rambling explanation at a press conference of why he was withdrawing - citing press plots against him - astonished official Washington. A White House aide told a reporter: 'Most of us were glued to the tube, our mouths open in shock.'
President Bill Clinton took extraordinary care over Admiral Inman's nomination. By moving him into the Pentagon to replace Les Aspin, the White House wanted to defuse criticism of its national security policy, which looked ragged after setbacks in Bosnia, Somalia and Haiti. It also wanted to appease the armed forces - hostile to Mr Clinton since he was elected - by appointing somebody who was a popular member of the military establishment.
It did not work. What President Clinton billed as a demonstration of decisive government has turned into a fiasco. A disadvantage of appointing an establishment insider, who confessed - almost boasted - of voting for George Bush in 1992, is that he had no loyalty to Mr Clinton. In Admiral Inman's lengthy explanation of why he was stepping aside yesterday there were few mentions of Mr Clinton.
So bizarre and petty were Admiral Inman's declared reasons for quitting that they fuelled suspicions they were a smoke-screen for another motive. In the 11 years since he resigned as CIA deputy director, he has had what the Wall Street Journal called a 'tortuous' business career. The British defence contractor Ferranti was brought down by paying an excessive price for ISC, a fraudulent company run by James Guerin, whom Admiral Inman had befriended.
It was the Admiral Inman's lack of business success - although he promised to bring the lessons he had learnt in the private sector to the Pentagon - that helped ignite the criticism he did face. But, as he himself admitted, his critics were few and his appointment faced no significant opposition. Nor, supposing he feared the revelation of some political or business time-bomb in his past, would he be likely to mask it by producing such half-baked conspiracy theories. His own career is in ruins. His allegations of plots against him are widely dismissed as goofy. The Senate Republican leader, Robert Dole, said the allegation that he had done a deal with New York Times columnist William Safire to oppose the Inman nomination in return for Mr Safire attacking Mr Clinton over business dealings in Arkansas was 'fantasy'.
Can the White House bounce back by appointing a new defence secretary with enough stature to overshadow Admiral Inman's retreating form? Mr Clinton might want somebody like General Colin Powell, the universally popular former chairman of the Joint Chiefs of Staff. But General Powell clashed with Mr Clinton over ending the ban on homosexuals in the military. He may not, in Admiral Inman's famous phrase, feel a sufficient 'level of comfort' with the administration to go back to the Pentagon.
Mr Clinton could also opt for a safe pair of hands, such as Willam Perry, deputy Defense Secretary, or James Woolsey, CIA director. Another candidate could be the former New Hampshire senator, Warren Rudman. But none of the three is likely, on past performance, to get a firm grip on the Pentagon, whose budget is critical to cost-cutting. Mr Aspin was no radical at Defense but he was still deeply resented by the military as representing the post- Cold War world in which their future is under scrutiny.
American military officers who have taken political office in the past - such as Alexander Haig and Admiral Jonathan Howe - have sometimes self-destructed when appointed to sensitive posts. For 30 years Admiral Inman was cocooned from criticism as a senior intelligence official. He never grew a political skin thick enough to protect him from Mr Safire's barbs.