He also remembered Mills' lighter side. As in the night he and a confederate crept up on a Marine standing watch, tossed a dummy grenade into the post, and videotaped him as he dove for cover.
"It sounds cruel to anyone who doesn't understand," Nelson said. "That's how Marines act. … It was hilarious."
Communities across the United States remembered the nation's war dead Monday in ceremonies at cemeteries, memorials and monuments.
"Captain Sara Cullen had a smile that could light up a room and a love of country that led her to West Point," Obama said. "And after graduation, Sara became a Black Hawk pilot — and married a former Black Hawk pilot.
"She was just 27 years old when she and four other soldiers were killed in a helicopter crash during a training mission near Kandahar. This past April, Sara was laid to rest here, in Section 60."
Obama then named others interred at Arlington, and concluded: "Today, we remember their service. Today, just steps from where these brave Americans lie in eternal peace, we declare, as a proud and grateful nation, that their sacrifice will never be forgotten."
Service members with Maryland ties who have died in action or training since Memorial Day 2012:
Marine Sgt. Julian C. Chase, Edgewater; Afghanistan, May 28, 2012
Marine Lance Cpl. Eugene C. Mills III, Laurel; Afghanistan, June 22, 2012
Army Staff Sgt. Daniel A. Rodriguez, Baltimore; Afghanistan, July 18, 2012
Army Staff Sgt. Brandon R. Pepper, Baltimore; Afghanistan, July 21, 2012
Navy Special Warfare Operator Petty Officer 1st Class Patrick D. Feeks, Edgewater; Afghanistan, Aug. 16, 2012
Army Sgt. David V. Williams, 24, Frederick; Afghanistan, Aug. 18, 2012
Navy Diver 2nd Class Ryan Harris, 23, Gladstone, Mo.; Aberdeen Proving Ground, Feb. 26, 2013
Navy Diver 1st Class James Reyher, 28, Caldwell, Ohio; Aberdeen Proving Ground, Feb. 26, 2013
Army Capt. Sara Knutson-Cullen, 27, Eldersburg; Afghanistan, March 11, 2013
Navy Lt. j.g. Valerie Cappelaere Delaney, 26, Ellicott City; Harrington, Wash., March 11, 2013
Marine Lance Cpl. William Taylor Wild IV, 21, Severna Park; March 18, 2013
Source: Department of Defense