President Joe Biden made an impromptu visit to the Vietnam Veterans Memorial late Monday afternoon in Washington to mark National Vietnam War Veterans Day. 

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The president and first lady Jill Biden laid a bouquet of flowers and stood in silence at one of the memorial's famed long black granite walls, polished to a high finish and etched with the names of more than 58,000 Americans who died in the war.'

President Joe Biden makes a tracing of Cpl. Dennis F. Shine's name after laying flowers at the Vietnam Veterans Memorial in honor of Vietnam War Veterans Day on Monday, March 29, 2021, in Washington. (AP Photo/Evan Vucci)

President Joe Biden makes a tracing of Cpl. Dennis F. Shine's name after laying flowers at the Vietnam Veterans Memorial in honor of Vietnam War Veterans Day on Monday, March 29, 2021, in Washington. (AP Photo/Evan Vucci)

The president then traced the name of Dennis F. Shine, according to the White House.

It was not immediately clear why the president chose Shine, a 21-year-old Massachusetts man who was killed in Vietnam in 1969.

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March 29 marks the 48th anniversary of the departure of the last U.S. combat troops from the war zone. The day commemorates the date in 1973 when the U.S. Military Assistance Command in Vietnam was disestablished.

The Associated Press contributed to this report.