-- Stanley Karnow, the award-winning author and journalist who wrote a definitive book about the Vietnam War, worked on an accompanying documentary and later won a Pulitzer for a history of the Philippines, died Sunday morning. He was 87.

Karnow, who had congestive heart failure, died in his sleep at his home in Potomac, Md., said son Michael Karnow.

A Paris-based correspondent for Time magazine early in his career, Karnow was assigned in 1958 to Hong Kong as bureau chief for Southeast Asia and soon arrived in Vietnam, when the American presence was still confined to a small core of advisers. In 1959, Karnow reported on the first two American deaths in Vietnam, not suspecting that tens of thousands would follow.

Into the 1970s, Karnow would cover the war off and on for Time, The Washington Post and other publications and then draw upon his experience for an epic PBS documentary and for the million-selling "Vietnam: A History," published in 1983 and widely regarded as an essential, even-handed summation.

Karnow's "In Our Image," a companion to a PBS documentary on the Philippines, won the Pulitzer in 1990. His other books included "Mao and China," which in 1973 received a National Book Award nomination, and "Paris in The Fifties," a memoir published in 1997.

A fellow Vietnam reporter, Morley Safer, would describe Karnow as the embodiment of "the wise old Asian hand." Karnow was known for his precision and research – his Vietnam book reaches back to ancient times – and his willingness to see past his own beliefs. He was a critic of the Vietnam War (and a name on President Nixon's enemies list) who still found cruelty and incompetence among the North Vietnamese. His friendship with Philippines leader Corazon Aquino did not stop him from criticizing her presidency.

A salesman's son, Karnow was born in New York in 1925 and by high school was writing radio plays and editing the school's paper, a job he also held at the Harvard Crimson. He first lived in Asia during World War II when he served throughout the region in the Army Air Corps. Back in the U.S., he majored in European history and literature at Harvard, from which he graduated in 1947.

Enchanted by French culture, and by the romance of Paris set down by Americans Ernest Hemingway and Henry Miller, Karnow set out for Europe after leaving school not for any particular purpose, but simply because it was there. "I went to Paris, planning to stay for the summer. I stayed for 10 years," he wrote in "Paris in the Fifties."

He began sending dispatches to a Connecticut weekly, where the owner was a friend, and in 1950 was hired as a researcher at Time. Promoted to correspondent, he would cover strikes, race car driving and the beginning of the French conflict with Algeria, but also interviewed Audrey Hepburn ("a memorable if regrettably brief encounter") fashion designer Christian Dior and director John Huston, who smoked cigars, knocked back Irish whiskies and rambled about the meaning of Humphrey Bogart. Friends and acquaintances included Norman Mailer, James Baldwin and John Kenneth Galbraith.

Bernard Kalb, a journalist, former State Department spokesman and longtime friend who met Karnow when they were both working in Hong Kong in the 1950s, said Karnow described journalism as the only profession "in which you can be an adolescent all your life."

"You never lose your enthusiasm and the depths of curiosity to engage with the world. That's what it means," Kalb told The Associated Press on Sunday. "Stanley took those particular drives of adolescence all through his life."

Karnow's first book was the text for "Southeast Asia," an illustrated Life World Library release published in 1962, before the U.S. committed ground troops to Vietnam. It was partly a Cold War time capsule, preoccupied with Communist influence, but was also skeptical enough of official policy to anticipate the fall of a key American ally, South Vietnamese president Ngo Dihn Diem, an event that helped lead to greater American involvement.

Like so many others, Karnow initially supported the war and believed in the "domino theory," which asserted that if South Vietnam were to fall to communism its neighbors would too.

But by war's end, Karnow agreed with the soldier asked by a reporter in 1968 what he thought of the conflict: "It stinks," was the reply.

"Vietnam: A History" was published in 1983 and coincided with a 13-part PBS documentary series. Like much of his work, Karnow's book combined historical research, firsthand observations and thorough reporting, including interviews with top officials on both sides of the war. Decades later, it remained read and taught alongside such classics as David Halberstam's "The Best and the Brightest" and Michael Herr's "Dispatches."

"There are not many carefully delineated judgments in the book. But that is more a comment than the criticism it might be, for Mr. Karnow does not claim to have reached a sweeping verdict on the war," Douglas Pike, a former U.S. government official in Vietnam who became a leading authority on the war, wrote for The New York Times in a 1983 review.

"Because he has a sharp eye for the illustrative moment and a keen ear for the telling quote, his book is first-rate as a popular contribution to understanding the war. And that is what he meant it to be."

The PBS series won six Emmys, a Peabody and a Polk and was the highest-rated documentary at the time for public television, with an average of 9.7 million viewers per episode. Along with much praise came criticism from the left and right. The liberal weekly The Nation faulted Karnow for "little analysis and much waffling." Conservatives were so angered by the documentary that PBS agreed to let the right-wing Accuracy in Media air a rebuttal, "Television's Vietnam: The Real Story," which in turn was criticized as a show of weakness by PBS.

Karnow completed no books after "Paris in the Fifties." He attempted a study of Asians in the U.S., which he abandoned; a history of Jewish humor that never advanced beyond an outline; and a second memoir, with such working titles as "Interesting Times" and "Out of Asia." He also cared for his ailing wife, Annette, who died of cancer in 2009. A previous marriage, to Claude Sarraute (daughter of French novelist Nathalie Sarraute), ended in divorce in 1955. Karnow had three children.

He was often called on for speeches, panel discussions and television appearances and asked for his opinions on current affairs. One query came in 2009, through his old friend Richard Holbrooke, at the time the U.S. special envoy to Afghanistan. Holbrooke wanted advice on U.S. policy in Afghanistan and put Karnow on the phone with Gen. Stanley McChrystal, the top U.S. commander. Karnow and the general discussed similarities between the wars in Afghanistan and Vietnam.

"What did we learn from Vietnam?" Karnow later told the AP. "We learned that we shouldn't have been there in the first place."

___

Associated Press writer Ben Nuckols in Washington contributed to this report.

Also on HuffPost:

  • Sepulveda Ferrari

    FILE - In this July 14, 1965, file photo, U.S. Army nurses Capt. Gladys E. Sepulveda, left, of Ponce, Puerto Rico, and 2nd Lt. Lois Ferrari, of Pittsburgh, Pa., rest on sandbags at Cam Ranh Bay in South Vietnam, during the Vietnam War. They two were waiting transportation to Nha Trang, to work in the 8th field hospital. (AP Photo, File)

  • Madame Ngo Dinh Nhu Tran Le Xuan

    FILE - This Aug. 1963 photo shows Tran Le Xuan, known as Madame Ngo Dinh Nhu in unknown location. Madame Nhu, the outspoken beauty who served as South Vietnam's unofficial first lady early on in the Vietnam War and earned the nickname "Dragon Lady" for her harsh criticism of protesting Buddhist monks and communist sympathizers, has died at age 86, a Rome funeral home said Wednesday, April 27, 2011. (AP Photo/File)

  • Members of the U.S. Army's 3rd Infantry Regiment "The Old Guard," hold folded flags at the start of burial services for U.S. Army Captain James M. Johnstone, of Baton Rouge, La., Wednesday, Dec. 12, 2012, at Arlington National Cemetery in Arlington, Va. The remains of the Vietnam-era soldier killedÜin the war were identified over forty years after Johnstone's airplane crashed in Laos in 1966. (AP Photo/Jacquelyn Martin)

  • Leon Panetta

    Defense Secretary Leon Panetta leaves the podium after speaking at the groundbreaking ceremony for the Vietnam Veterans Memorial Fund's next project to honor veterans, the Education Center at The Wall, Wednesday, Nov. 28, 2012, in Washington. The center will tell the stories of 58,000 soldiers who died in the Vietnam War and will honor fallen soldiers from the wars in Iraq and Afghanistan. (AP Photo/Manuel Balce Ceneta)

  • Vietnam War

    FILE - B52 high altitude bombers leave condensation trails while passing the town of Cai Lay in the Mekong Delta on Sept. 29, 1972, moments after unleashing bombs on a suspected enemy positions. (AP Photo/Nick Ut, File)

  • Horst Faas

    FILE - Associated Press photographer Horst Faas is shown in this undated file photo in Ca Mau, Vietnam. The recent deaths of Faas, correspondent George Esper, writer Roy Essoyan and correspondent Malcolm Browne represent the slipping away of a generation of war reporters that brought the reality of the conflict to the living rooms of America in often horrifying close-up and inspired scores of combat journalists in their wake. (AP Photo/File)

  • FILE - In this Jan. 7, 1965 file photo, Associated Press Saigon correspondent Malcolm Browne goes on patrol near Binh Hia, South Vietnam with South Vietnamese troops. The recent deaths of Browne, photographer Horst Faas, correspondent George Esper, and writer Roy Essoyan represent the slipping away of a generation of war reporters that brought the reality of the conflict to the living rooms of America in often horrifying close-up and inspired scores of combat journalists in their wake. (AP Photo, File)

  • George Esper

    FILE - In this Jan. 1, 1966 file photo, AP special correspondent George Esper poses with a Vietnamese boy in Quang Ngai Province, south of Da Nang. The recent deaths of Esper, photographer Horst Faas, correspondent Malcolm Browne, and writer Roy Essoyan represent the slipping away of a generation of war reporters that brought the reality of the conflict to the living rooms of America in often horrifying close-up and inspired scores of combat journalists in their wake. (AP Photo, file)

  • Vietnam Monk

    FILE - In this June 11, 1963 file photo, one of a series taken by then AP Saigon correspondent Malcom Browne, Thich Quang Duc, a Buddhist monk, burns himself to death on a Saigon street to protest alleged persecution of Buddhists by the South Vietnamese government. Browne, acclaimed for his trenchant reporting of the Vietnam War and a photo of a Buddhist monk's suicide by fire that shocked the Kennedy White House into a critical policy re-evaluation, died Monday night, Aug. 27, 2012 at a hospital in New Hampshire, not far from his home in Thetford, Vt. He was 81. (AP Photo/Malcolm Browne)

  • FILE - In this June 27, 1963 file photo. AP Saigon correspondent Malcolm Browne interviews Quang Lien, leading spokesman for the Xa Loi Buddhist pagoda in Saigon. Browne, acclaimed for his trenchant reporting of the Vietnam War and a photo of a Buddhist monk's suicide by fire that shocked the Kennedy White House into a critical policy re-evaluation, died Monday night, Aug. 27, 2012 at a hospital in New Hampshire, not far from his home in Thetford, Vt. He was 81. (AP Photo)

  • FILE - In this June 8, 1972 file photo taken by Associated Press photographer Huynh Cong "Nick" Ut, a Vietnamese man and woman carry severely burned children down Route 1 after a misdirected napalm attack by South Vietnamese pilots in the village of Trang Bang, South Vietnam. The aerial attack was intended for enemy forces on the outskirts of the village. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • FILE - In this June 8, 1972 file photo taken by Associated Press photographer Huynh Cong "Nick" Ut, a Skyraider, a propeller driven plane of the Vietnamese Airforce (VNAF) 518th Squadron, drops one bomb with incendiary napalm and white phosphorus jelly over Trang Bang village. It only took a second for Ut to snap the iconic black-and-white image of 9-year-old Phan Thi Kim Phuc, one of the victims of the napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • FILE - This June 8, 1972 file photo taken by Associated Press photographer Huynh Cong "Nick" Ut, shows bombs with a mixture of napalm and white phosphorus jelly dropped by Vietnamese Air Force Skyraider bombers explode across Route 1, amidst homes and in front of the Cao Dai temple on the outskirts of Trang Bang, Vietnam. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut)

  • FILE-This Sept. 20, 1970, file photo taken by Associated Press photographer, Huynh Cong "Nick" Ut, shows a Cambodian soldier on an operation in Vietnam. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut)

  • FILE- In this early 1968 file photo taken by Associated Press photographer, Huynh Cong "Nick" Ut, the body of a man lies beside a road in the Saigon area of Vietnam during the Tet Offensive. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • photojournalist

    FILE - In this Aug. 17, 1989 file photo, Phan Thi Kim Phuc embraces Associated Press staff photographer Nick Ut during a reunion in Havana, Cuba. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Jim Caccavo, File)

  • FILE -In this August 20, 1970, file photo taken by Associated Press photographer Huynh Cong "Nick" Ut, a line of South Vietnamese marines moves across a shallow branch of the Mekong River during an operation near Neak Luong, Cambodia. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • FILE- In this May 8, 1970, file photo taken by Associated Press photographer Huynh Cong "Nick" Ut, a South Vietnamese tank crew abandons tank after it was hit by B40 rockets and automatic weapons two miles north of Svay Rieng in eastern Cambodia. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • FILE- In this early 1968 file photo, taken by Associated Press photographer Huynh Cong "Nick" Ut, journalists photograph a body in the Saigon area in early 1968, during the Tet Offensive. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • FILE- In this April 6, 1969, file photo, taken by Associated Press Photographer Huynh Cong "Nick" Ut, youthful civil defense militiamen leap into the flooded Nipa Palm grove near Saigon, Vietnam. It only took a second for Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • FILE- In this June 1970 file photo, taken by Associated Press photographer Huynh Cong "Nick" Ut, south Vietnamese Marines rush to the point where descending U.S. Army helicopter will pick them up after a sweep east of the Cambodian town of Prey-Veng during the Vietnam War. It only took a second for Associated Press Photographer Huynh Cong "Nick" Ut to snap the iconic black-and-white image of Phan Thi Kim Phuc after a napalm attack in 1972, but it communicated the horrors of the Vietnam War in a way words could never describe, helping to end one of America's darkest eras. (AP Photo/Nick Ut, File)

  • Barack Obamam, Leon Panetta, Eric Shinseki

    Secretary of Veterans Affairs Eric Shinseki, left, and Secretary of Defense Leon Panetta talk as they sit on stage with Vietnam Veterans Memorial Wall behind them before President Barack Obama speaks during a Memorial Day ceremony at the Vietnam Veterans Memorial Wall to commemorate the 50th anniversary of the Vietnam War on, Monday, May 28, 2012, in Washington. (AP Photo/Carolyn Kaster)

  • Vienam Veterans Memorial

    A visitor to the Vietnam Veteran's Memorial touches the name of a fallen soldier etched on the wall of the memorial in Washington, Friday, May 25, 2012. On Monday, the Vietnam Veterans Memorial Wall will begin the national commemoration of the Vietnam War?s 50th anniversary. (AP Photo/Susan Walsh)

  • Vienam Veterans Memorial

    People take rubbings of names of fallen etched on the wall of the Vietnam Veteran's Memorial in Washington, Friday, May 25, 2012. On Monday, the Vietnam Veterans Memorial Wall will begin the national commemoration of the Vietnam War's 50th anniversary. (AP Photo/Susan Walsh)

  • Red Flegal

    Volunteer Red Flegal of New London, Pa., helps a visitor with a rubbing of a name} on the Vietnam Veteran's Memorial in Washington, Friday, May 25, 2012. On Monday, the Vietnam Veterans Memorial Wall will begin the national commemoration of the Vietnam War?s 50th anniversary. (AP Photo/Susan Walsh)

  • Vienam Veterans Memorial

    People take a rubbing of a name as they visit the Vietnam Veteran's Memorial in Washington, Friday, May 25, 2012. On Monday, the Vietnam Veterans Memorial Wall will begin the national commemoration of the Vietnam War?s 50th anniversary. (AP Photo/Susan Walsh)

  • Verlin Maglitz

    Vietnam veteran Verlin Maglitz of Jacksonville, Ill., pauses as he takes a rubbing of those he fought with in Vietnam during his visit to the Vietnam Veteran's Memorial in Washington, Friday, May 25, 2012. Maglitz was in the Army and served in Vietnam as part of the 101st Airborne Division and plans to take rubbings of approximately 45 of his friends. On Monday, the Vietnam Veterans Memorial Wall will begin the national commemoration of the Vietnam War?s 50th anniversary. (AP Photo/Susan Walsh)

  • FILE - In this Jan. 16, 1966 file photo taken by Associated Press photographer Horst Faas, Lt. Col. George Eyster of Florida is placed on a stretcher after being shot by a Viet Cong sniper at Trung Lap, South Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas, File)

  • FILE - In this Jan. 1, 1966 file photo taken by Associated Press photographer Horst Faas, women and children crouch in a muddy canal as they take cover from intense Viet Cong fire at Bao Trai, about 20 miles west of Saigon, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • FILE - In this July 15, 1966 file photo taken by Associated Press photographer Horst Faas, U.S. Marines scatter as a CH-46 helicopter burns, background, after it was shot down near the demilitarized zone (DMZ) between North and South Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • FILE - In this Jan. 1, 1966 file photo, two South Vietnamese children gaze at an American paratrooper holding an M79 grenade launcher as they cling to their mothers who huddle against a canal bank for protection from Viet Cong sniper fire in the Bao Trai area, 20 miles west of Saigon, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • FILE - In this March 1965 file photo shot by Associated Press photographer Horst Faas, hovering U.S. Army helicopters pour machine gun fire into the tree line to cover the advance of South Vietnamese ground troops in an attack on a Viet Cong camp 18 miles north of Tay Ninh, Vietnam, northwest of Saigon near the Cambodian border. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas, File)

  • FILE - In this March 30, 1965 file photo taken by Associated Press photographer Horst Faas, injured Vietnamese receive aid as they lie on the street after a bomb explosion outside the U.S. Embassy in Saigon, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas, File)

  • FILE - In this March 1973 file photo taken by Associated Press photographer Horst Faas, American prisoners of war look through barred wooden doors at the last detention camp at Ly Nam De Street in Hanoi, North Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas, File)

  • FILE - In this July 15, 1966 file photo taken by Associated Press photographer Horst Faas, U.S. Marines scatter as a CH-46 helicopter burns, background, after it was shot down near the demilitarized zone (DMZ) between North and South Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • FILE - In this Aug. 1962 file photo shot by Associated Press photographer Horst Faas, South Vietnamese government troops from the 2nd Battalion of the 36th Infantry sleep in a U.S. Navy troop carrier on their way back to the Provincial capital of Ca Mau, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas, File)

  • FILE - In this Jan. 9, 1964 file photo one of several shot by Associated Press photographer Horst Faas, earning him the first of two Pulitzer Prizes, a South Vietnamese soldier uses the end of a dagger to beat a farmer for allegedly supplying government troops with inaccurate information about the movement of Viet Cong guerrillas in a village west of Saigon, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, has died May 10, 2012. He was 79. (AP Photo/Horst Faas, File)

  • FILE - In this June 1965 file photo shot by Associated Press photographer Horst Faas, South Vietnamese civilians, among the few survivors of two days of heavy fighting, huddle together in the aftermath of an attack by government troops to retake the post at Dong Xoai, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • File - In this December 1965 file photo shot by Associated Press photographer Horst Faas, a U.S. 1st Division soldier guards Route 7 as Vietnamese women and school children return home to the village of Xuan Dien from Ben Cat, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, died Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • FILE - In this Jan. 1, 1966 file photo taken by Associated Press photographer Horst Faas, women and children crouch in a muddy canal as they take cover from intense Viet Cong fire at Bao Trai, about 20 miles west of Saigon, Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • April 2, 1967 flle photo

    FILE - In this April 2, 1967 file photo shot by Associated Press photographer Horst Faas, wounded U.S. soldiers are treated on a battle field in Vietnam. Faas, a prize-winning combat photographer who carved out new standards for covering war with a camera and became one of the world's legendary photojournalists in nearly half a century with The Associated Press, Thursday May 10, 2012. He was 79. (AP Photo/Horst Faas)

  • In a May 4, 1970 file photo, a group of youths cluster around a wounded person as Ohio National Guardsmen, wearing gas masks, hold their weapons in the background, on Kent State University campus in Kent, Ohio. Members of the Guards killed four students and injured nine during a campus protest against the Vietnam War. The U.S. Justice Department, citing "insurmountable legal and evidentiary barriers," won't reopen its investigation into the deadly 1970 shootings by Ohio National Guardsmen during a Vietnam War protest at Kent State University. Assistant Attorney General Thomas Perez discussed the obstacles in a letter to Alan Canfora, a wounded student who requested that the investigation be reopened. The Justice Department said Tuesday, April 24, 2012 it would not comment beyond the letter. (AP Photo/Douglas Moore, File)