Maj. Jay T. Aubin was stationed at a Marine base in Okinawa when he was invited to join the elite corps that pilots the presidential helicopter, Marine One. But before he could start ferrying President Bush on hops from the White House lawn, Aubin was offered a different honor: an assignment as an instructor in night flight for helicopter pilots at the Marine Corps Air Station in Yuma, Ariz.

It was not in Aubin's nature to shirk anything the Marines asked of him during his 18-year career. As a boy in a small Maine town, he had loved the small airplanes his father and grandfather tinkered with and flew. As a high school senior, he created a year-long boot camp for himself, eager to be physically groomed by graduation, when he would become a Marine.

And so Aubin, 36, shipped out last month to Kuwait not from Washington but from Arizona. He once told his father that night vision in the desert "was so spooky and strange and all sparkly with the sand flying around." It was dark early Thursday when a CH-46 Sea Knight helicopter containing U.S. and British troops crashed slightly over the Kuwaiti border from Iraq, making Aubin one of the first four U.S. casualties of a new war.

In Baltimore, Houston and St. Anne, Ill., as well as Aubin's native Winslow, Maine, families gathered to begin mourning the war's costs in a particularly personal way.

By Friday's end, the Defense Department had confirmed that two additional Marines had been killed in Iraq, marking the first casualties of engagement with Iraqi soldiers. The government did not identify the pair. Defense officials said one Marine, from the 1st Marine Division, died in a firefight as he led his infantry platoon on an assault on an oil pumping station. The second, from the 1st Marine Expeditionary Force, died in combat near the port of Umm Qasr.

Aboard the helicopter, which went down in bad weather for reasons the military has not disclosed, was Cpl. Brian M. Kennedy, 25. He was originally from Port Clyde, Maine, but had lived in Texas; he was a Marine of less than three years who loved rock climbing and sailing and the craggy coast of his home state. His mother, Melissa Derbyshire, told a local newspaper she understood her son's sacrifice in the Middle East even before the war began, from his accounts of four-hour walks to a shower and three-hour waits for a precious telephone call home.

And Staff Sgt. Kendall D. Waters-Bey, 29, of Baltimore, a helicopter maintenance specialist who had attended Northern High School and leaves behind a son.

And Capt. Ryan A. Beaupre, 30, of St. Anne, who was to have been the best man at his younger brother's November wedding. Friday, standing in front of the brick house where Beaupre and his three siblings had grown up, his sister, Alyse, recalled that he always had rebuffed nagging that it was his turn to find a wife, by saying it would conflict with his commitment to the military. "We used to say he was married to the Marines and having an affair with his surfboard," Alyse Beaupre said of her brother's passions.

A town of 1,300 surrounded by the farm fields of north-central Illinois, St. Anne seemed plunged into a collective grief. "God Bless America and Special Blessings for the Beaupres," said a sign strung outside Finally Mary's, a local restaurant.

"This hits a little too close to home, " said Jerry Little, 32, a steelworker who never met Beaupre and has lived in St. Anne for just three years. "I don't know how people are going to deal with this. We know we have to be over there, but there is a lot of anger and sadness."

Greta Bruhn has lived in St. Anne for 48 years. Friday, she was fastening star-spangled bows on trees and light posts outside her house, across the street from the Beaupres. "He was super, just super, the best you could find," she said.

Several hundred miles away, at Aubin's mother's house, an uncle said he heard that Beaupre and Aubin had become close friends. The uncle, Peter Willette, said Aubin had last visited for about three weeks in July, returning from Marine Corps Base Camp S.D. Butler, en route to Yuma. His instructor's stint, Willette said, was to last three years, before Aubin was to take up duties with Marine One.

When he visited, Aubin had not formally been told he would be sent to the Middle East. "But he had a pretty good idea," Willette said. "As good a pilot as he was, he was handpicked for a lot of these things. He talked to each of us individually. He knew he would be right on the front line."

The eldest of three sons, Aubin always struck his closest brother, Joel, 34, as an overachiever. He was selected student of the month, then student of the year as a senior at Skowhegan Area High School. He was athletic, drawn to football, baseball and wrestling. But his first love was flight -- with his grandfather, an airplane mechanic, and his father, Thomas, who ran gas stations and restaurants but spent his spare time buying, selling and flying planes.

He became a mechanic during his first four years in the Marines, and met his wife, Rhonda, a fellow Marine at the time, with whom he would have a daughter and a son, now 10 and 7 years old. They returned to Maine, where he received an associate's degree in machine tooling, then a bachelor's degree in business management. His schooling done, he immediately reenlisted.

Just before leaving for Kuwait six weeks ago, he had a conversation with his mother, Nancy Chamberlain, his uncle recalled. He told her, "You know where I'll be. You know how important it is for us to be there, and if anything happens to me just know that I'm doing what I love."

It was 7 a.m. Friday when a Marine major and a chaplain arrived at Chamberlain's doorstep, the government's official emissaries of mournful news. The major, Chris Ross, apologized if his military bearing cracked. "He wanted us to excuse him if he didn't seem smooth," Willette said. "He was as choked up as we were. It was this gentleman's first time he ever had to do it."

Staff writer Alan Cooperman, research editor Margot Williams and special correspondent Kari Lydersen in St. Anne, Ill., contributed to this report.

Kenneth Waters-Bey, 10, salutes as he holds a photo of his father, Staff Sgt. Kendall D. Waters-Bey, of Baltimore, who was one of four U.S. Marines killed in a CH-46 helicopter crash in Kuwait on Thursday. Cpl. Brian M. Kennedy Maj. Jay T. Aubin