Veterans Affairs Secretary Eric K. Shinseki faced tough questions from a Senate panel Thursday about the state of his department after allegations that some VA health clinics have cooked their books to cover up treatment delays.

The American Legion, the nation’s largest veterans-service group, has called on Shinseki and two other top Department of Veterans Affairs officials to resign over the record-keeping controversy.

Below are answers to a few key questions about these latest troubles:

Who is Eric Shinseki?

Shinseki is a retired four-star Army general and Vietnam War veteran who received two Purple Hearts for injuries he sustained during that conflict. He has headed VA since January 2009.

Veterans Affairs Secretary Eric Shinseki testified before the Senate Thursday on VA health clinics allegedly covering up treatment delays. (The Washington Post)

As Army chief of staff, Shinseki famously clashed with top Pentagon officials over how many troops would be needed to occupy Iraq. He told the Senate Armed Services Committee in 2003 that the effort would require “several hundred thousand soldiers,” but former defense secretary Donald H. Rumsfeld said the estimate would “prove to be high.”

Shinseki retired from the Army shortly after the fall of Baghdad in 2003, having served 38 years in the military.

Why is he in the hot seat?

The Senate Veterans’ Affairs Committee called Shinseki to testify after multiple reports of alleged preventable deaths and attempts to cover up treatment delays at VA health clinics. Whistleblowers have said a Phoenix VA hospital kept delays off the books with secret waiting lists that allegedly included dozens of patients who died while waiting for care.

Similarly, a report from the VA Office of the Medical Inspector said a department clinic in Fort Collins, Colo., falsified appointment records to give the impression that staff doctors saw patients within the agency’s goal of 14 days.

Veterans groups also have expressed concerns about a deadly outbreak of Legionnaires’ disease at a Pittsburgh VA hospital in 2012 and reports that several patients died at an Atlanta clinic because of mismanagement. A VA inspector general’s report said the clinic was not sufficiently addressing patient safety.

VA also has a long-standing problem with disability claims that have remained in the system for at least 125 days without a determination. The Obama administration has set a goal of eliminating that inventory by 2015. VA reported this year that it had reduced the amount by 44 percent since the number of claims reached a high of more than 600,000 in 2012.

What has VA done about the alleged coverups?

The department’s inspector general has launched an investigation of the allegations, and Shin­seki ordered face-to-face audits of scheduling practices at all VA health clinics. The secretary has promised to take action on the reviews when they are complete.

In the meantime, Shinseki has placed three of the Phoenix hospital’s executives on administrative leave “until further notice.”

How widespread is this problem?

The attention has focused on the allegations of wrongdoing in Phoenix and Fort Collins, but Senate Veterans’ Affairs Committee Chairman Bernie Sanders (I-Vt.) said Thursday that similar scandals have surfaced in at least 10 states, based on evidence provided by the American Legion.

How long has VA struggled with wait times?

Sen. Patty Murray (D-Wash.) noted during Thursday’s hearing that multiple Government Accountability Office reports dating to 2000 have highlighted VA treatment delays. She said the department’s inspector general looked at the issue in 2005, 2007 and 2012, determining each time that schedulers were not following VA policy.

The 2012 report said the department had not developed a reliable or accurate way of knowing whether its clinics were providing timely access to mental health care.

Where does the White House stand?

The White House has said President Obama remains confident in Shinseki’s ability to lead VA and to take appropriate actions once the investigations are complete.

Obama on Wednesday directed his deputy chief of staff, Rob Nabors, to evaluate VA scheduling practices, signaling the White House’s growing concern over the alleged coverups.

Nabors is perhaps best known for his work on the failed fiscal cliff deal. As the White House’s chief congressional liaison, he developed a reputation as a methodical wonk and quiet dealmaker who loves lists and despises leaks, according to a 2012 Washington Post profile.