Secretary of Veterans Affairs Eric K. Shinseki knows adversity.

As a soldier in Vietnam, he was seriously wounded twice, the second time during a second tour of duty when he stepped on a land mine and lost half of his right foot. That should have ended his Army career. Instead, he asked for, and received, a waiver to stay on active duty.

His determination turned blunt force in 2003 when, as Army chief of staff, Shinseki clashed with then-Defense Secretary Donald Rumsfeld over the George W. Bush administration's Iraq war strategy. Although history would prove Shinseki correct in his assessment, he retired several months later, after 38 years in the Army.

The uniform was put away, but not the soldier.

Now, the first Japanese American to become a four-star general is in a firestorm, facing a president "madder than hell" and an investigation, whose early results are expected next week, that could determine whether his leadership will survive reports that VA employees have been covering up long wait times for medical care.

But Shinseki, 71, has held this job since 2009, longer than any of his predecessors, and doesn't give up easily.

"His tenacity in the face of adversity is really very strong," said Richard Halloran, author of "My Name Is Shinseki and I Am a Soldier."

Some doubt that Shinseki, in spite of a long and distinguished military career, can turn around the VA.

When he told lawmakers last week that he too was "mad as hell" about the wait lists, he came in for ridicule for his low-key, seemingly passive manner.

"If he's that mad, he needs a better war face," Derek Bennett, chief of staff of the Iraq and Afghanistan Veterans of America, said on Twitter.

"Your 'mad as hell' face looks a lot like your 'Oh, we're out of orange juice' face," comedian Jon Stewart said.

But that's Shinseki, those who know him say: a retired general with a master's degree in English literature who doesn't pound the table or raise his voice.

"Ric Shinseki doesn't get 'mad as hell,'" said retired Gen. Barry McCaffrey, who has known him since their days at West Point in the 1960s. "He is determined, focused and wants to factually understand a problem so he can get a sensible solution. He fired 3,000 VA employees last year. He will take action and hold people accountable."

Joseph Galloway, a retired military writer who has known Shinseki for more than two decades, called him a "quiet, soft-spoken soldier. No bluster. No BS. Probably the least political four-star I ever met. He prefers to quietly lead by example."

Shinseki has asked for patience while the VA inspector general investigates reports of excessive wait times and falsification of records at the department's medical facilities, and he pledged to veterans last week to redouble efforts to "earn your trust." Twenty-six VA sites are under investigation.

President Obama said this week that Shinseki had "put his heart and soul" into trying to improve veterans' services. "If he does not think he can do a good job on this and if he thinks he's let our veterans down, then I'm sure that he is not going to be interested in continuing to serve," the president added.

While the American Legion and a number of Republican and a few Democratic lawmakers have called for Shinseki's resignation, those who know him best say he is likely to remain in the job so long as Obama has confidence in him.

Few dispute Shinseki's devotion to veterans.

As Army chief of staff, Shinseki called every soldier who lost a limb, retired Army Sgt. Maj. Jack L. Tilley said.

"More than once, he has said, 'I have been carried out of battle twice on the backs of American soldiers. You can imagine my love for them,'" said Halloran, Shinseki's biographer.