Driving in circles around Washington, D.C., Beth Belle and Leesa Philippon are having one of their Lucy-and-Ethel moments, like a couple of zany pals on a road trip. "This is Constitution, right? Isn't it?" says Belle, a willowy, ebullient 52. "You go left, at 17th," says Philippon, 45, slow-speaking and ethereal, wrestling a map. "I think."

They laugh, enjoying their own ditziness. But the mood turns pensive as they pull through the gates of Arlington National Cemetery. "I try to come every Sunday; it's so beautiful," Belle says. "We have a special pass," notes Philippon, softly. "Because our boys are here."

Belle winds her Honda through the stirring expanse of more than 300,000 headstones: Presidents and buck privates, celebrities and former slaves, from the Civil War to last week. "This is Section 60," she says. "For Iraq and Afghanistan." The friends park and walk to the end of a muddy aisle of graves, then bow their heads. On the left lies Belle's son, Marine Lance Corporal Nicholas C. Kirven, a practical joker so fashion-conscious his squad buddies nicknamed him Paris; on the right, Philippon's boy, Marine Lance Corporal Lawrence R. Philippon, a star hockey goalie in high school who carried the flag at Ronald Reagan's funeral and quoted whole scenes from Forrest Gump. Both were shot and killed while leading assaults on insurgent hideouts—Nick, cut down at 21 in an Afghan mountain cave; Larry, 22, machine-gunned in the face near al-Qa'im, Iraq. And both died May 8, 2005.

On Mother's Day.

That brutal coincidence is what brought Belle and Philippon together. You'd think they've known each other forever—they all but finish each other's sentences. In fact the pair live some 350 miles apart, Belle in Fairfax, Va., Philippon in West Hartford, Conn., and never met before their sons were laid to rest. The day after she buried Larry, Philippon noticed Nick's marker next to his and felt a connection with this fallen Marine's mother, whoever she might be. Finding Belle through a newspaper Web site, she called her and they began an e-mail correspondence. And so, from the darkest place, Belle and Philippon have formed a bond that is at once universal and singular—two women who now spend Christmases together and go shopping for summer tops at Loehmann's, but also call one another in the middle of the night when grief overwhelms sleep.

"Losing a child is an actual physical pain, like you exhale but don't inhale again—your breath is gone," says Belle. "When I talk to Leesa, it's just like, 'Oh, I get it. That's how I feel too.' The connection is such a gift."

Belle recalls her 51st birthday, her first one without Nicholas. Her husband, Michael, had tickets to a musical for the two of them and their other children, Pride, 25, and Joseph, 16. "But Nicholas wasn't there. And I didn't want to celebrate," she says. "But I couldn't tell anyone because I didn't want to rain on their parade. So I called Leesa. Her birthday had been two weeks earlier, and she said she didn't want to celebrate. Because we knew there would be no card or phone call from Nick or Larry that birthday or any more to come, forever. I could be completely honest with her and not feel guilty."

In lighter moments, they swap stories about the boys—their first day of school, first loose tooth, first moment in Marine dress blues. Nick's room in the Belles' airy Georgian home is just as he left it: soccer and basketball trophies, mounted buck's head, but also, arrayed on a shelf over his bed, a Dickensian Christmas village. "He was a guy's guy but soft also," Belle says. "Even as a teenager, he'd always tell us he loved us."

Always drawn to the military, her son joined up a month after 9/11. "Nicholas said, 'I know you're scared, but I'll always be with you,'" Belle says. He was sent to Afghanistan as an assault climber, scaling mountains and rooting out caves. "People said, 'You're so lucky he's going to Afghanistan,'" she adds, ruefully. "'It's safe there.'"

Unlike Nick, Larry Philippon came from a military family—Leesa and husband Ray met while in the Army. "From the time he was small, Larry was in constant motion," says the reserved Ray, 45, a bond manager. He was a tough kid—a lacrosse defenseman as well as a hockey player—but tender. "There were always more guys around, but Larry let me in to play the boys' games," recalls his sister Emilee, 20. "He had a heart for everybody."

Larry, who joined up in 2003, loved being a Marine—even basic training. "But he'd call me every single day," Philippon says. "Marines aren't perfect—he might be at a bar, but he'd call just to say, 'Hi, Mom.'" In Iraq, he seemed to have the time of his life, mugging goofily for almost every photo. "A Marine told me," Emilee says, "that 10 minutes before he was killed—while they were taking gunfire—Larry said, 'I love this. I live for this.'"

The day he died was not only Mother's Day but the Philippons' 24th wedding anniversary. Leesa cried for much of it. "We went to Wal-Mart for some socks to ship to Larry," she recalls. "In the car I said, 'Ray, I feel so bad I have three beautiful children and I think about the poor families who lost kids in the war."

A little before 9 p.m. that night she went out to walk the dog. That's when she saw a military family's most dreaded sight: two uniformed men approaching the door. "I saw the silhouettes of their hats, and I ran in screaming, for Ray—I knew then and there," she says.

At the same time an eerily similar scene played out in Fairfax. "All day I felt something wrong," Belle says. "I hadn't heard from Nicholas. I knew he'd do everything he could to call me for Mother's Day. I kept checking my e-mail. Then at 8:57 p.m. the doorbell rang. They kept asking, 'Are you Elizabeth Belle?' I wouldn't answer—I knew what they were going to tell me."

The fallen Marines were buried with full military honors; Nicholas on May 16, Larry the next day. When Philippon saw Nick's marker, she posted a message to the Belles' page on Legacy.com, a site with a section for families of the fallen. The moms exchanged e-mails and met at Arlington the next month. "There weren't many words, just a lot of hugs," recalls Belle, a women's clothing merchandiser. Adds Philippon: "Just to hold another mother and know what she's going through."

On the 8th of each month for the next year, they'd light candles and write one another. That Christmas the Philippons came to Fairfax and stayed with the Belles. It would be the first of eight visits. "We opened presents and prayed," says Philippon, a floor secretary at a Veterans Administration hospital. "We cried a lot, exchanged pictures and videos of our sons and their funerals."

Over time, their bond has expanded beyond shared grief—brightening their lives to include everyday things like work, their other kids and, yes, shopping. "That's always a fiasco," Philippon says. "We'll try on shirts, come out, laugh at each other, then I'll wind up buying the shirt she had picked out. Or that time in Loehmann's: I was holding her place in line, they're shutting the store and she's still running to the dressing room."

The other family members have made connections too. When they get together, Michael, 56, Nicholas's stepfather since he was 6 months old, and Ray watch sports or talk politics—both staunchly support the President and are active in the Tragedy Assistance Program for Survivors (TAPS), an organization for bereaved families and friends of those in the military, speaking at gatherings and going to funerals. "But we're not like our wives—we don't e-mail each other saying, 'I had a bad day,'" deadpans Michael, a stocky home builder with a penetrating gaze, as Beth and Leesa break up laughing. For their part, the Philippons' son Bryan, 17, and Joseph Belle stay in touch by text-messaging and have helped each other through rough patches. "Ah, Jobes," Bryan says, chuckling at his pal's nickname. "We went to the Cheesecake Factory that first time, and he seemed like a cool kid. We're both into video games—Halo, the one where you shoot aliens." Adds Joseph: "We talk about our brothers, how their deaths affected our schoolwork—I thought no one else knew what I was going through. But we also talk about lacrosse—we both played varsity—girls and life."

The bond between their younger sons brings joy to Philippon and Belle, who think their older boys would have liked each other too. Behind their sons' graves is a cherry tree, now in bloom, that they planted last year. "Long after we're gone, it will still be here," Philippon says. For now the two moms are here for each other. "When I see it's Leesa's number on my cell phone, it's such a relief," Belle says. "I finally have someone who understands my soul."